diff --git a/sky/engine/bindings/jni/dart_jni.cc b/sky/engine/bindings/jni/dart_jni.cc
index 563805f7390e58161cb70bd664670d82f30e951f..d7a049fc6b1c14b25f81f2f2505729b9a76a2d9b 100644
--- a/sky/engine/bindings/jni/dart_jni.cc
+++ b/sky/engine/bindings/jni/dart_jni.cc
@@ -16,7 +16,6 @@
 #include "sky/engine/tonic/dart_args.h"
 #include "sky/engine/tonic/dart_binding_macros.h"
 #include "sky/engine/tonic/dart_converter.h"
-#include "sky/engine/wtf/MakeUnique.h"
 
 namespace blink {
 
@@ -49,7 +48,7 @@ DartJniJvmData* g_jvm_data = nullptr;
 
 void CreateIsolateData() {
   static_cast<FlutterDartState*>(DartState::Current())->set_jni_data(
-      WTF::MakeUnique<DartJniIsolateData>());
+      std::unique_ptr<DartJniIsolateData>(new DartJniIsolateData()));
 }
 
 DartJniIsolateData* IsolateData() {
diff --git a/sky/engine/bindings/jni/dart_jni.h b/sky/engine/bindings/jni/dart_jni.h
index d9ee55dd41bbc2b3e12c8ea96fcc2d6e31815165..04653e89a98dfb286f17b7cb926c30647bc8ad66 100644
--- a/sky/engine/bindings/jni/dart_jni.h
+++ b/sky/engine/bindings/jni/dart_jni.h
@@ -9,10 +9,9 @@
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_utils.h"
+#include "base/memory/ref_counted.h"
 #include "sky/engine/tonic/dart_library_natives.h"
 #include "sky/engine/tonic/dart_wrappable.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/RefCounted.h"
 
 #define ENTER_JNI()                                                            \
   JNIEnv* env = base::android::AttachCurrentThread();                          \
diff --git a/sky/engine/bindings/jni/jni_api.cc b/sky/engine/bindings/jni/jni_api.cc
index 325bafd484239b5ed55062729eaedbf7d55e9bdd..211cf114f3e5f57ed4f02d85e16bc28c38ed5901 100644
--- a/sky/engine/bindings/jni/jni_api.cc
+++ b/sky/engine/bindings/jni/jni_api.cc
@@ -20,7 +20,7 @@ int64_t JniApi::FromReflectedField(const JniObject* field) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -36,16 +36,16 @@ int64_t JniApi::FromReflectedMethod(const JniObject* method) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
-PassRefPtr<JniObject> JniApi::GetApplicationContext() {
+scoped_refptr<JniObject> JniApi::GetApplicationContext() {
   ENTER_JNI();
   return JniObject::Create(env, base::android::GetApplicationContext());
 }
 
-PassRefPtr<JniObject> JniApi::GetClassLoader() {
+scoped_refptr<JniObject> JniApi::GetClassLoader() {
   ENTER_JNI();
   return JniObject::Create(env, DartJni::class_loader());
 }
diff --git a/sky/engine/bindings/jni/jni_api.h b/sky/engine/bindings/jni/jni_api.h
index d339b89ad0bf56ad3b93111de4c82b37b48b18c3..49a4a82b47db4d9d283c6b1ba2dcb7118f03ec54 100644
--- a/sky/engine/bindings/jni/jni_api.h
+++ b/sky/engine/bindings/jni/jni_api.h
@@ -15,8 +15,8 @@ class JniApi {
  public:
   static int64_t FromReflectedField(const JniObject* field);
   static int64_t FromReflectedMethod(const JniObject* method);
-  static PassRefPtr<JniObject> GetApplicationContext();
-  static PassRefPtr<JniObject> GetClassLoader();
+  static scoped_refptr<JniObject> GetApplicationContext();
+  static scoped_refptr<JniObject> GetClassLoader();
 };
 
 } // namespace blink
diff --git a/sky/engine/bindings/jni/jni_array.cc b/sky/engine/bindings/jni/jni_array.cc
index fe17e34e5e93af9252cfcd54563e7549770a89ee..f0498a136599bf3a7cdf8dc8b05edf60d5e277cc 100644
--- a/sky/engine/bindings/jni/jni_array.cc
+++ b/sky/engine/bindings/jni/jni_array.cc
@@ -28,7 +28,7 @@ jsize JniArray::GetLength() {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -45,7 +45,7 @@ JniObjectArray::JniObjectArray(JNIEnv* env, jobjectArray array)
 JniObjectArray::~JniObjectArray() {
 }
 
-PassRefPtr<JniObjectArray> JniObjectArray::Create(const JniClass* clazz,
+scoped_refptr<JniObjectArray> JniObjectArray::Create(const JniClass* clazz,
                                                   jsize length) {
   Dart_Handle exception = nullptr;
   {
@@ -55,15 +55,15 @@ PassRefPtr<JniObjectArray> JniObjectArray::Create(const JniClass* clazz,
                                              nullptr);
     if (CheckJniException(env, &exception)) goto fail;
 
-    return adoptRef(new JniObjectArray(env, array));
+    return new JniObjectArray(env, array);
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
-PassRefPtr<JniObject> JniObjectArray::GetArrayElement(jsize index) {
+scoped_refptr<JniObject> JniObjectArray::GetArrayElement(jsize index) {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -76,7 +76,7 @@ PassRefPtr<JniObject> JniObjectArray::GetArrayElement(jsize index) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -93,7 +93,7 @@ void JniObjectArray::SetArrayElement(jsize index, const JniObject* value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -105,7 +105,7 @@ JniBooleanArray::JniBooleanArray(JNIEnv* env, jbooleanArray array)
 JniBooleanArray::~JniBooleanArray() {
 }
 
-PassRefPtr<JniBooleanArray> JniBooleanArray::Create(jsize length) {
+scoped_refptr<JniBooleanArray> JniBooleanArray::Create(jsize length) {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -113,11 +113,11 @@ PassRefPtr<JniBooleanArray> JniBooleanArray::Create(jsize length) {
     jbooleanArray array = env->NewBooleanArray(length);
     if (CheckJniException(env, &exception)) goto fail;
 
-    return adoptRef(new JniBooleanArray(env, array));
+    return new JniBooleanArray(env, array);
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -134,7 +134,7 @@ bool JniBooleanArray::GetArrayElement(jsize index) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return false;
 }
 
@@ -152,7 +152,7 @@ void JniBooleanArray::SetArrayElement(jsize index, bool value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -164,7 +164,7 @@ JniByteArray::JniByteArray(JNIEnv* env, jbyteArray array)
 JniByteArray::~JniByteArray() {
 }
 
-PassRefPtr<JniByteArray> JniByteArray::Create(jsize length) {
+scoped_refptr<JniByteArray> JniByteArray::Create(jsize length) {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -172,11 +172,11 @@ PassRefPtr<JniByteArray> JniByteArray::Create(jsize length) {
     jbyteArray array = env->NewByteArray(length);
     if (CheckJniException(env, &exception)) goto fail;
 
-    return adoptRef(new JniByteArray(env, array));
+    return new JniByteArray(env, array);
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -193,7 +193,7 @@ int64_t JniByteArray::GetArrayElement(jsize index) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return false;
 }
 
@@ -211,7 +211,7 @@ void JniByteArray::SetArrayElement(jsize index, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -223,7 +223,7 @@ JniCharArray::JniCharArray(JNIEnv* env, jcharArray array)
 JniCharArray::~JniCharArray() {
 }
 
-PassRefPtr<JniCharArray> JniCharArray::Create(jsize length) {
+scoped_refptr<JniCharArray> JniCharArray::Create(jsize length) {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -231,11 +231,11 @@ PassRefPtr<JniCharArray> JniCharArray::Create(jsize length) {
     jcharArray array = env->NewCharArray(length);
     if (CheckJniException(env, &exception)) goto fail;
 
-    return adoptRef(new JniCharArray(env, array));
+    return new JniCharArray(env, array);
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -252,7 +252,7 @@ int64_t JniCharArray::GetArrayElement(jsize index) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return false;
 }
 
@@ -270,7 +270,7 @@ void JniCharArray::SetArrayElement(jsize index, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -282,7 +282,7 @@ JniShortArray::JniShortArray(JNIEnv* env, jshortArray array)
 JniShortArray::~JniShortArray() {
 }
 
-PassRefPtr<JniShortArray> JniShortArray::Create(jsize length) {
+scoped_refptr<JniShortArray> JniShortArray::Create(jsize length) {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -290,11 +290,11 @@ PassRefPtr<JniShortArray> JniShortArray::Create(jsize length) {
     jshortArray array = env->NewShortArray(length);
     if (CheckJniException(env, &exception)) goto fail;
 
-    return adoptRef(new JniShortArray(env, array));
+    return new JniShortArray(env, array);
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -311,7 +311,7 @@ int64_t JniShortArray::GetArrayElement(jsize index) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return false;
 }
 
@@ -329,7 +329,7 @@ void JniShortArray::SetArrayElement(jsize index, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -341,7 +341,7 @@ JniIntArray::JniIntArray(JNIEnv* env, jintArray array)
 JniIntArray::~JniIntArray() {
 }
 
-PassRefPtr<JniIntArray> JniIntArray::Create(jsize length) {
+scoped_refptr<JniIntArray> JniIntArray::Create(jsize length) {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -349,11 +349,11 @@ PassRefPtr<JniIntArray> JniIntArray::Create(jsize length) {
     jintArray array = env->NewIntArray(length);
     if (CheckJniException(env, &exception)) goto fail;
 
-    return adoptRef(new JniIntArray(env, array));
+    return new JniIntArray(env, array);
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -370,7 +370,7 @@ int64_t JniIntArray::GetArrayElement(jsize index) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return false;
 }
 
@@ -388,7 +388,7 @@ void JniIntArray::SetArrayElement(jsize index, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -400,7 +400,7 @@ JniLongArray::JniLongArray(JNIEnv* env, jlongArray array)
 JniLongArray::~JniLongArray() {
 }
 
-PassRefPtr<JniLongArray> JniLongArray::Create(jsize length) {
+scoped_refptr<JniLongArray> JniLongArray::Create(jsize length) {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -408,11 +408,11 @@ PassRefPtr<JniLongArray> JniLongArray::Create(jsize length) {
     jlongArray array = env->NewLongArray(length);
     if (CheckJniException(env, &exception)) goto fail;
 
-    return adoptRef(new JniLongArray(env, array));
+    return new JniLongArray(env, array);
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -429,7 +429,7 @@ int64_t JniLongArray::GetArrayElement(jsize index) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return false;
 }
 
@@ -447,7 +447,7 @@ void JniLongArray::SetArrayElement(jsize index, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -459,7 +459,7 @@ JniFloatArray::JniFloatArray(JNIEnv* env, jfloatArray array)
 JniFloatArray::~JniFloatArray() {
 }
 
-PassRefPtr<JniFloatArray> JniFloatArray::Create(jsize length) {
+scoped_refptr<JniFloatArray> JniFloatArray::Create(jsize length) {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -467,11 +467,11 @@ PassRefPtr<JniFloatArray> JniFloatArray::Create(jsize length) {
     jfloatArray array = env->NewFloatArray(length);
     if (CheckJniException(env, &exception)) goto fail;
 
-    return adoptRef(new JniFloatArray(env, array));
+    return new JniFloatArray(env, array);
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -488,7 +488,7 @@ double JniFloatArray::GetArrayElement(jsize index) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return false;
 }
 
@@ -506,7 +506,7 @@ void JniFloatArray::SetArrayElement(jsize index, double value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -518,7 +518,7 @@ JniDoubleArray::JniDoubleArray(JNIEnv* env, jdoubleArray array)
 JniDoubleArray::~JniDoubleArray() {
 }
 
-PassRefPtr<JniDoubleArray> JniDoubleArray::Create(jsize length) {
+scoped_refptr<JniDoubleArray> JniDoubleArray::Create(jsize length) {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -526,11 +526,11 @@ PassRefPtr<JniDoubleArray> JniDoubleArray::Create(jsize length) {
     jdoubleArray array = env->NewDoubleArray(length);
     if (CheckJniException(env, &exception)) goto fail;
 
-    return adoptRef(new JniDoubleArray(env, array));
+    return new JniDoubleArray(env, array);
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -547,7 +547,7 @@ double JniDoubleArray::GetArrayElement(jsize index) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return false;
 }
 
@@ -564,7 +564,7 @@ void JniDoubleArray::SetArrayElement(jsize index, double value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
diff --git a/sky/engine/bindings/jni/jni_array.h b/sky/engine/bindings/jni/jni_array.h
index 3ad6c39a7f0788a765afa4a6ad8e3867fd8abc11..4793738dd73a62aed66e1a45b5cb1f0a0f5ad097 100644
--- a/sky/engine/bindings/jni/jni_array.h
+++ b/sky/engine/bindings/jni/jni_array.h
@@ -33,8 +33,8 @@ class JniObjectArray : public JniArray {
  public:
   ~JniObjectArray() override;
 
-  static PassRefPtr<JniObjectArray> Create(const JniClass* clazz, jsize length);
-  PassRefPtr<JniObject> GetArrayElement(jsize index);
+  static scoped_refptr<JniObjectArray> Create(const JniClass* clazz, jsize length);
+  scoped_refptr<JniObject> GetArrayElement(jsize index);
   void SetArrayElement(jsize index, const JniObject* value);
 
  private:
@@ -48,7 +48,7 @@ class JniBooleanArray : public JniArray {
  public:
   ~JniBooleanArray() override;
 
-  static PassRefPtr<JniBooleanArray> Create(jsize length);
+  static scoped_refptr<JniBooleanArray> Create(jsize length);
   bool GetArrayElement(jsize index);
   void SetArrayElement(jsize index, bool value);
 
@@ -63,7 +63,7 @@ class JniByteArray : public JniArray {
  public:
   ~JniByteArray() override;
 
-  static PassRefPtr<JniByteArray> Create(jsize length);
+  static scoped_refptr<JniByteArray> Create(jsize length);
   int64_t GetArrayElement(jsize index);
   void SetArrayElement(jsize index, int64_t value);
 
@@ -78,7 +78,7 @@ class JniCharArray : public JniArray {
  public:
   ~JniCharArray() override;
 
-  static PassRefPtr<JniCharArray> Create(jsize length);
+  static scoped_refptr<JniCharArray> Create(jsize length);
   int64_t GetArrayElement(jsize index);
   void SetArrayElement(jsize index, int64_t value);
 
@@ -93,7 +93,7 @@ class JniShortArray : public JniArray {
  public:
   ~JniShortArray() override;
 
-  static PassRefPtr<JniShortArray> Create(jsize length);
+  static scoped_refptr<JniShortArray> Create(jsize length);
   int64_t GetArrayElement(jsize index);
   void SetArrayElement(jsize index, int64_t value);
 
@@ -108,7 +108,7 @@ class JniIntArray : public JniArray {
  public:
   ~JniIntArray() override;
 
-  static PassRefPtr<JniIntArray> Create(jsize length);
+  static scoped_refptr<JniIntArray> Create(jsize length);
   int64_t GetArrayElement(jsize index);
   void SetArrayElement(jsize index, int64_t value);
 
@@ -123,7 +123,7 @@ class JniLongArray : public JniArray {
  public:
   ~JniLongArray() override;
 
-  static PassRefPtr<JniLongArray> Create(jsize length);
+  static scoped_refptr<JniLongArray> Create(jsize length);
   int64_t GetArrayElement(jsize index);
   void SetArrayElement(jsize index, int64_t value);
 
@@ -138,7 +138,7 @@ class JniFloatArray : public JniArray {
  public:
   ~JniFloatArray() override;
 
-  static PassRefPtr<JniFloatArray> Create(jsize length);
+  static scoped_refptr<JniFloatArray> Create(jsize length);
   double GetArrayElement(jsize index);
   void SetArrayElement(jsize index, double value);
 
@@ -153,7 +153,7 @@ class JniDoubleArray : public JniArray {
  public:
   ~JniDoubleArray() override;
 
-  static PassRefPtr<JniDoubleArray> Create(jsize length);
+  static scoped_refptr<JniDoubleArray> Create(jsize length);
   double GetArrayElement(jsize index);
   void SetArrayElement(jsize index, double value);
 
diff --git a/sky/engine/bindings/jni/jni_class.cc b/sky/engine/bindings/jni/jni_class.cc
index c42bdbcda0e81306d47b6dc93275a9bc14f3aaf0..77d2e6fb3dd3241e9ea005af7be9dd4edf131a0e 100644
--- a/sky/engine/bindings/jni/jni_class.cc
+++ b/sky/engine/bindings/jni/jni_class.cc
@@ -18,7 +18,7 @@ JniClass::JniClass(JNIEnv* env, jclass clazz)
 JniClass::~JniClass() {
 }
 
-PassRefPtr<JniClass> JniClass::FromName(const char* name) {
+scoped_refptr<JniClass> JniClass::FromName(const char* name) {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -28,15 +28,15 @@ PassRefPtr<JniClass> JniClass::FromName(const char* name) {
     ScopedJavaLocalRef<jclass> clazz = DartJni::GetClass(env, name);
     if (CheckJniException(env, &exception)) goto fail;
 
-    return adoptRef(new JniClass(env, clazz.obj()));
+    return new JniClass(env, clazz.obj());
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
-PassRefPtr<JniClass> JniClass::FromClassObject(const JniObject* clazz) {
+scoped_refptr<JniClass> JniClass::FromClassObject(const JniObject* clazz) {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -49,11 +49,11 @@ PassRefPtr<JniClass> JniClass::FromClassObject(const JniObject* clazz) {
       goto fail;
     }
 
-    return adoptRef(new JniClass(env, static_cast<jclass>(class_object)));
+    return new JniClass(env, static_cast<jclass>(class_object));
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -69,7 +69,7 @@ intptr_t JniClass::GetFieldId(const char* name, const char* sig) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -85,7 +85,7 @@ intptr_t JniClass::GetStaticFieldId(const char* name, const char* sig) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -101,7 +101,7 @@ intptr_t JniClass::GetMethodId(const char* name, const char* sig) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -117,11 +117,11 @@ intptr_t JniClass::GetStaticMethodId(const char* name, const char* sig) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
-PassRefPtr<JniObject> JniClass::NewObject(
+scoped_refptr<JniObject> JniClass::NewObject(
     jmethodID methodId, const std::vector<Dart_Handle>& args) {
   Dart_Handle exception = nullptr;
   {
@@ -138,7 +138,7 @@ PassRefPtr<JniObject> JniClass::NewObject(
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -154,11 +154,11 @@ bool JniClass::IsAssignable(const JniClass* clazz) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return false;
 }
 
-PassRefPtr<JniObject> JniClass::GetStaticObjectField(jfieldID fieldId) {
+scoped_refptr<JniObject> JniClass::GetStaticObjectField(jfieldID fieldId) {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -170,7 +170,7 @@ PassRefPtr<JniObject> JniClass::GetStaticObjectField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -186,7 +186,7 @@ bool JniClass::GetStaticBooleanField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return false;
 }
 
@@ -202,7 +202,7 @@ int64_t JniClass::GetStaticByteField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -218,7 +218,7 @@ int64_t JniClass::GetStaticCharField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -234,7 +234,7 @@ int64_t JniClass::GetStaticShortField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -250,7 +250,7 @@ int64_t JniClass::GetStaticIntField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -266,7 +266,7 @@ int64_t JniClass::GetStaticLongField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -282,7 +282,7 @@ double JniClass::GetStaticFloatField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -298,7 +298,7 @@ double JniClass::GetStaticDoubleField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -315,7 +315,7 @@ void JniClass::SetStaticObjectField(jfieldID fieldId, const JniObject* value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -332,7 +332,7 @@ void JniClass::SetStaticBooleanField(jfieldID fieldId, bool value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -348,7 +348,7 @@ void JniClass::SetStaticByteField(jfieldID fieldId, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -364,7 +364,7 @@ void JniClass::SetStaticCharField(jfieldID fieldId, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -380,7 +380,7 @@ void JniClass::SetStaticShortField(jfieldID fieldId, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -396,7 +396,7 @@ void JniClass::SetStaticIntField(jfieldID fieldId, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -412,7 +412,7 @@ void JniClass::SetStaticLongField(jfieldID fieldId, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -428,7 +428,7 @@ void JniClass::SetStaticFloatField(jfieldID fieldId, double value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -444,11 +444,11 @@ void JniClass::SetStaticDoubleField(jfieldID fieldId, double value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
-PassRefPtr<JniObject> JniClass::CallStaticObjectMethod(
+scoped_refptr<JniObject> JniClass::CallStaticObjectMethod(
     jmethodID methodId, const std::vector<Dart_Handle>& args) {
   Dart_Handle exception = nullptr;
   {
@@ -466,7 +466,7 @@ PassRefPtr<JniObject> JniClass::CallStaticObjectMethod(
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -488,7 +488,7 @@ bool JniClass::CallStaticBooleanMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return false;
 }
 
@@ -510,7 +510,7 @@ int64_t JniClass::CallStaticByteMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -532,7 +532,7 @@ int64_t JniClass::CallStaticCharMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -554,7 +554,7 @@ int64_t JniClass::CallStaticShortMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -576,7 +576,7 @@ int64_t JniClass::CallStaticIntMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -598,7 +598,7 @@ int64_t JniClass::CallStaticLongMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -620,7 +620,7 @@ double JniClass::CallStaticFloatMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -642,7 +642,7 @@ double JniClass::CallStaticDoubleMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -663,7 +663,7 @@ void JniClass::CallStaticVoidMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
diff --git a/sky/engine/bindings/jni/jni_class.h b/sky/engine/bindings/jni/jni_class.h
index 19428fe8fccc57b9b1490579017ed1d410a304c0..497037a501ec3cf89e086b5991adf64756203f62 100644
--- a/sky/engine/bindings/jni/jni_class.h
+++ b/sky/engine/bindings/jni/jni_class.h
@@ -8,10 +8,9 @@
 #include <jni.h>
 
 #include "base/android/jni_android.h"
+#include "base/memory/ref_counted.h"
 #include "sky/engine/bindings/jni/jni_object.h"
 #include "sky/engine/tonic/dart_wrappable.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/RefCounted.h"
 
 namespace blink {
 
@@ -23,8 +22,8 @@ class JniClass : public JniObject {
  public:
   ~JniClass() override;
 
-  static PassRefPtr<JniClass> FromName(const char* className);
-  static PassRefPtr<JniClass> FromClassObject(const JniObject* clazz);
+  static scoped_refptr<JniClass> FromName(const char* className);
+  static scoped_refptr<JniClass> FromClassObject(const JniObject* clazz);
 
   jclass java_class() const { return static_cast<jclass>(object_.obj()); }
 
@@ -33,12 +32,12 @@ class JniClass : public JniObject {
   intptr_t GetMethodId(const char* name, const char* sig);
   intptr_t GetStaticMethodId(const char* name, const char* sig);
 
-  PassRefPtr<JniObject> NewObject(jmethodID methodId,
+  scoped_refptr<JniObject> NewObject(jmethodID methodId,
                                   const std::vector<Dart_Handle>& args);
 
   bool IsAssignable(const JniClass* clazz);
 
-  PassRefPtr<JniObject> GetStaticObjectField(jfieldID fieldId);
+  scoped_refptr<JniObject> GetStaticObjectField(jfieldID fieldId);
   bool GetStaticBooleanField(jfieldID fieldId);
   int64_t GetStaticByteField(jfieldID fieldId);
   int64_t GetStaticCharField(jfieldID fieldId);
@@ -58,7 +57,7 @@ class JniClass : public JniObject {
   void SetStaticFloatField(jfieldID fieldId, double value);
   void SetStaticDoubleField(jfieldID fieldId, double value);
 
-  PassRefPtr<JniObject> CallStaticObjectMethod(
+  scoped_refptr<JniObject> CallStaticObjectMethod(
       jmethodID methodId, const std::vector<Dart_Handle>& args);
   bool CallStaticBooleanMethod(jmethodID methodId,
                                const std::vector<Dart_Handle>& args);
diff --git a/sky/engine/bindings/jni/jni_object.cc b/sky/engine/bindings/jni/jni_object.cc
index 90ec07354bb8c6c009bd6b7bf34822e3d923c72f..8dfe3a1c4af60bf3e259759888e4cf3702e5f88d 100644
--- a/sky/engine/bindings/jni/jni_object.cc
+++ b/sky/engine/bindings/jni/jni_object.cc
@@ -21,7 +21,7 @@ JniObject::JniObject(JNIEnv* env, jobject object)
 JniObject::~JniObject() {
 }
 
-PassRefPtr<JniObject> JniObject::Create(JNIEnv* env, jobject object) {
+scoped_refptr<JniObject> JniObject::Create(JNIEnv* env, jobject object) {
   if (object == nullptr)
     return nullptr;
 
@@ -55,10 +55,10 @@ PassRefPtr<JniObject> JniObject::Create(JNIEnv* env, jobject object) {
     result = new JniObject(env, object);
   }
 
-  return adoptRef(result);
+  return result;
 }
 
-PassRefPtr<JniClass> JniObject::GetObjectClass() {
+scoped_refptr<JniClass> JniObject::GetObjectClass() {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -66,15 +66,15 @@ PassRefPtr<JniClass> JniObject::GetObjectClass() {
     jclass clazz = env->GetObjectClass(java_object());
     if (CheckJniException(env, &exception)) goto fail;
 
-    return adoptRef(new JniClass(env, clazz));
+    return new JniClass(env, clazz);
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
-PassRefPtr<JniObject> JniObject::GetObjectField(jfieldID fieldId) {
+scoped_refptr<JniObject> JniObject::GetObjectField(jfieldID fieldId) {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -86,7 +86,7 @@ PassRefPtr<JniObject> JniObject::GetObjectField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -102,7 +102,7 @@ bool JniObject::GetBooleanField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return false;
 }
 
@@ -118,7 +118,7 @@ int64_t JniObject::GetByteField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -134,7 +134,7 @@ int64_t JniObject::GetCharField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -150,7 +150,7 @@ int64_t JniObject::GetShortField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -166,7 +166,7 @@ int64_t JniObject::GetIntField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -182,7 +182,7 @@ int64_t JniObject::GetLongField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -198,7 +198,7 @@ double JniObject::GetFloatField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -214,7 +214,7 @@ double JniObject::GetDoubleField(jfieldID fieldId) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -231,7 +231,7 @@ void JniObject::SetObjectField(jfieldID fieldId, const JniObject* value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -248,7 +248,7 @@ void JniObject::SetBooleanField(jfieldID fieldId, bool value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -264,7 +264,7 @@ void JniObject::SetByteField(jfieldID fieldId, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -280,7 +280,7 @@ void JniObject::SetCharField(jfieldID fieldId, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -296,7 +296,7 @@ void JniObject::SetShortField(jfieldID fieldId, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -312,7 +312,7 @@ void JniObject::SetIntField(jfieldID fieldId, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -328,7 +328,7 @@ void JniObject::SetLongField(jfieldID fieldId, int64_t value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -344,7 +344,7 @@ void JniObject::SetFloatField(jfieldID fieldId, double value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
@@ -360,11 +360,11 @@ void JniObject::SetDoubleField(jfieldID fieldId, double value) {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
-PassRefPtr<JniObject> JniObject::CallObjectMethod(
+scoped_refptr<JniObject> JniObject::CallObjectMethod(
     jmethodID methodId,
     const std::vector<Dart_Handle>& args) {
   Dart_Handle exception = nullptr;
@@ -383,7 +383,7 @@ PassRefPtr<JniObject> JniObject::CallObjectMethod(
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -405,7 +405,7 @@ bool JniObject::CallBooleanMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return false;
 }
 
@@ -427,7 +427,7 @@ int64_t JniObject::CallByteMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -449,7 +449,7 @@ int64_t JniObject::CallCharMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -471,7 +471,7 @@ int64_t JniObject::CallShortMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -493,7 +493,7 @@ int64_t JniObject::CallIntMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -515,7 +515,7 @@ int64_t JniObject::CallLongMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -537,7 +537,7 @@ double JniObject::CallFloatMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -559,7 +559,7 @@ double JniObject::CallDoubleMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return 0;
 }
 
@@ -580,7 +580,7 @@ void JniObject::CallVoidMethod(jmethodID methodId,
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return;
 }
 
diff --git a/sky/engine/bindings/jni/jni_object.h b/sky/engine/bindings/jni/jni_object.h
index 67018538c8205ab4503e5c819dd09b258bc1f43e..afa20d242ce74fcc3f8cfd9aa29dbb289b5c08e0 100644
--- a/sky/engine/bindings/jni/jni_object.h
+++ b/sky/engine/bindings/jni/jni_object.h
@@ -8,28 +8,27 @@
 #include <jni.h>
 
 #include "base/android/jni_android.h"
+#include "base/memory/ref_counted.h"
 #include "sky/engine/tonic/dart_wrappable.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/RefCounted.h"
 
 namespace blink {
 
 class JniClass;
 
 // Wrapper that exposes a JNI jobject to Dart
-class JniObject : public ThreadSafeRefCounted<JniObject>, public DartWrappable {
+class JniObject : public base::RefCountedThreadSafe<JniObject>, public DartWrappable {
   DEFINE_WRAPPERTYPEINFO();
 
  public:
   ~JniObject() override;
 
-  static PassRefPtr<JniObject> Create(JNIEnv* env, jobject object);
+  static scoped_refptr<JniObject> Create(JNIEnv* env, jobject object);
 
   jobject java_object() const { return object_.obj(); }
 
-  PassRefPtr<JniClass> GetObjectClass();
+  scoped_refptr<JniClass> GetObjectClass();
 
-  PassRefPtr<JniObject> GetObjectField(jfieldID fieldId);
+  scoped_refptr<JniObject> GetObjectField(jfieldID fieldId);
   bool GetBooleanField(jfieldID fieldId);
   int64_t GetByteField(jfieldID fieldId);
   int64_t GetCharField(jfieldID fieldId);
@@ -49,8 +48,8 @@ class JniObject : public ThreadSafeRefCounted<JniObject>, public DartWrappable {
   void SetFloatField(jfieldID fieldId, double value);
   void SetDoubleField(jfieldID fieldId, double value);
 
-  PassRefPtr<JniObject> CallObjectMethod(jmethodID methodId,
-                                         const std::vector<Dart_Handle>& args);
+  scoped_refptr<JniObject> CallObjectMethod(jmethodID methodId,
+                                            const std::vector<Dart_Handle>& args);
   bool CallBooleanMethod(jmethodID methodId,
                          const std::vector<Dart_Handle>& args);
   int64_t CallByteMethod(jmethodID methodId,
diff --git a/sky/engine/bindings/jni/jni_string.cc b/sky/engine/bindings/jni/jni_string.cc
index edd0722c63c1fbdc0afc6719a51014f9f0ad938b..f4265723ab2a924ee36b7cadb89813433614e98d 100644
--- a/sky/engine/bindings/jni/jni_string.cc
+++ b/sky/engine/bindings/jni/jni_string.cc
@@ -18,7 +18,7 @@ jstring JniString::java_string() {
   return static_cast<jstring>(java_object());
 }
 
-PassRefPtr<JniString> JniString::Create(Dart_Handle dart_string) {
+scoped_refptr<JniString> JniString::Create(Dart_Handle dart_string) {
   Dart_Handle exception = nullptr;
   {
     ENTER_JNI();
@@ -27,11 +27,11 @@ PassRefPtr<JniString> JniString::Create(Dart_Handle dart_string) {
                                                     &exception);
     if (exception) goto fail;
 
-    return adoptRef(new JniString(env, java_string));
+    return new JniString(env, java_string);
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return nullptr;
 }
 
@@ -53,7 +53,7 @@ Dart_Handle JniString::GetText() {
   }
 fail:
   Dart_ThrowException(exception);
-  ASSERT_NOT_REACHED();
+  NOTREACHED();
   return Dart_Null();
 }
 
diff --git a/sky/engine/bindings/jni/jni_string.h b/sky/engine/bindings/jni/jni_string.h
index 16f241983262ad4103de3219f67efda36be209ba..cb9896f24a08cb181fa64acc4e6907211867da82 100644
--- a/sky/engine/bindings/jni/jni_string.h
+++ b/sky/engine/bindings/jni/jni_string.h
@@ -18,7 +18,7 @@ class JniString : public JniObject {
  public:
   ~JniString() override;
 
-  static PassRefPtr<JniString> Create(Dart_Handle dart_string);
+  static scoped_refptr<JniString> Create(Dart_Handle dart_string);
   Dart_Handle GetText();
 
  private:
diff --git a/sky/engine/core/compositing/Scene.cpp b/sky/engine/core/compositing/Scene.cpp
index 2e1feea677aad5affd599bfc754294a259588982..937b10c32b828df586e9a7d100eda67731a2d287 100644
--- a/sky/engine/core/compositing/Scene.cpp
+++ b/sky/engine/core/compositing/Scene.cpp
@@ -20,10 +20,10 @@ IMPLEMENT_WRAPPERTYPEINFO(ui, Scene);
 
 DART_BIND_ALL(Scene, FOR_EACH_BINDING)
 
-PassRefPtr<Scene> Scene::create(
+scoped_refptr<Scene> Scene::create(
     std::unique_ptr<flow::Layer> rootLayer,
     uint32_t rasterizerTracingThreshold) {
-  return adoptRef(new Scene(std::move(rootLayer), rasterizerTracingThreshold));
+  return new Scene(std::move(rootLayer), rasterizerTracingThreshold);
 }
 
 Scene::Scene(std::unique_ptr<flow::Layer> rootLayer,
diff --git a/sky/engine/core/compositing/Scene.h b/sky/engine/core/compositing/Scene.h
index 1f49ee1a63465c4c8a9fb52d78f7226d0d42bd1f..ed72269c28fb469c88bdf525a9811e250390f2fc 100644
--- a/sky/engine/core/compositing/Scene.h
+++ b/sky/engine/core/compositing/Scene.h
@@ -8,21 +8,20 @@
 #include <stdint.h>
 #include <memory>
 
+#include "base/memory/ref_counted.h"
 #include "flow/layers/layer_tree.h"
 #include "sky/engine/tonic/dart_wrappable.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/ThreadSafeRefCounted.h"
 #include "third_party/skia/include/core/SkPicture.h"
 
 namespace blink {
 class DartLibraryNatives;
 
-class Scene : public ThreadSafeRefCounted<Scene>, public DartWrappable {
+class Scene : public base::RefCountedThreadSafe<Scene>, public DartWrappable {
   DEFINE_WRAPPERTYPEINFO();
 
  public:
   ~Scene() override;
-  static PassRefPtr<Scene> create(
+  static scoped_refptr<Scene> create(
       std::unique_ptr<flow::Layer> rootLayer,
       uint32_t rasterizerTracingThreshold);
 
diff --git a/sky/engine/core/compositing/SceneBuilder.cpp b/sky/engine/core/compositing/SceneBuilder.cpp
index 6b634058331b582b7de550891d7fdf40247fd4a5..defed6dd762508382001b4c4d7d6ab1b68409cd3 100644
--- a/sky/engine/core/compositing/SceneBuilder.cpp
+++ b/sky/engine/core/compositing/SceneBuilder.cpp
@@ -214,14 +214,14 @@ void SceneBuilder::setRasterizerTracingThreshold(uint32_t frameInterval)
     m_currentRasterizerTracingThreshold = frameInterval;
 }
 
-PassRefPtr<Scene> SceneBuilder::build()
+scoped_refptr<Scene> SceneBuilder::build()
 {
     m_currentLayer = nullptr;
     int32_t threshold = m_currentRasterizerTracingThreshold;
     m_currentRasterizerTracingThreshold = 0;
-    RefPtr<Scene> scene = Scene::create(std::move(m_rootLayer), threshold);
+    scoped_refptr<Scene> scene = Scene::create(std::move(m_rootLayer), threshold);
     ClearDartWrapper();
-    return scene.release();
+    return std::move(scene);
 }
 
 } // namespace blink
diff --git a/sky/engine/core/compositing/SceneBuilder.h b/sky/engine/core/compositing/SceneBuilder.h
index 33e7916a5a71784bcbc64ad931c5eba337ab0162..4f1912655a330bd075e5f23085f2a5f7a0f5e567 100644
--- a/sky/engine/core/compositing/SceneBuilder.h
+++ b/sky/engine/core/compositing/SceneBuilder.h
@@ -8,6 +8,7 @@
 #include <stdint.h>
 #include <memory>
 
+#include "base/memory/ref_counted.h"
 #include "flow/layers/container_layer.h"
 #include "sky/engine/bindings/exception_state.h"
 #include "sky/engine/core/compositing/Scene.h"
@@ -21,17 +22,13 @@
 #include "sky/engine/core/painting/RRect.h"
 #include "sky/engine/tonic/dart_wrappable.h"
 #include "sky/engine/tonic/float64_list.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/ThreadSafeRefCounted.h"
 
 namespace blink {
 
-class SceneBuilder : public ThreadSafeRefCounted<SceneBuilder>, public DartWrappable {
+class SceneBuilder : public base::RefCountedThreadSafe<SceneBuilder>, public DartWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
-    static PassRefPtr<SceneBuilder> create() {
-      return adoptRef(new SceneBuilder());
-    }
+    static scoped_refptr<SceneBuilder> create() { return new SceneBuilder(); }
 
     ~SceneBuilder() override;
 
@@ -65,7 +62,7 @@ public:
 
     void setRasterizerTracingThreshold(uint32_t frameInterval);
 
-    PassRefPtr<Scene> build();
+    scoped_refptr<Scene> build();
 
     static void RegisterNatives(DartLibraryNatives* natives);
 
diff --git a/sky/engine/core/painting/Canvas.cpp b/sky/engine/core/painting/Canvas.cpp
index 0a0f07e0ea40e2d5a01ef742047bb4743451607a..e5ac0accd68fb312092a09ab31b1948448cf45ad 100644
--- a/sky/engine/core/painting/Canvas.cpp
+++ b/sky/engine/core/painting/Canvas.cpp
@@ -66,15 +66,15 @@ FOR_EACH_BINDING(DART_REGISTER_NATIVE)
   });
 }
 
-PassRefPtr<Canvas> Canvas::create(PictureRecorder* recorder,
-                                  double left,
-                                  double top,
-                                  double right,
-                                  double bottom) {
+scoped_refptr<Canvas> Canvas::create(PictureRecorder* recorder,
+                                     double left,
+                                     double top,
+                                     double right,
+                                     double bottom) {
     ASSERT(recorder);
     ASSERT(!recorder->isRecording());
-    PassRefPtr<Canvas> canvas = adoptRef(new Canvas(recorder->beginRecording(
-        SkRect::MakeLTRB(left, top, right, bottom))));
+    scoped_refptr<Canvas> canvas = new Canvas(recorder->beginRecording(
+        SkRect::MakeLTRB(left, top, right, bottom)));
     recorder->set_canvas(canvas.get());
     return canvas;
 }
diff --git a/sky/engine/core/painting/Canvas.h b/sky/engine/core/painting/Canvas.h
index 58058423e1d05a650c6222b4e464ea60f7ed2864..f31f7c2441bb882d2b38c23f4d07eb10dd1ad600 100644
--- a/sky/engine/core/painting/Canvas.h
+++ b/sky/engine/core/painting/Canvas.h
@@ -5,6 +5,7 @@
 #ifndef SKY_ENGINE_CORE_PAINTING_CANVAS_H_
 #define SKY_ENGINE_CORE_PAINTING_CANVAS_H_
 
+#include "base/memory/ref_counted.h"
 #include "sky/engine/bindings/exception_state.h"
 #include "sky/engine/core/painting/CanvasPath.h"
 #include "sky/engine/core/painting/Offset.h"
@@ -12,13 +13,11 @@
 #include "sky/engine/core/painting/Picture.h"
 #include "sky/engine/core/painting/PictureRecorder.h"
 #include "sky/engine/core/painting/Point.h"
-#include "sky/engine/core/painting/RRect.h"
 #include "sky/engine/core/painting/Rect.h"
+#include "sky/engine/core/painting/RRect.h"
 #include "sky/engine/core/painting/RSTransform.h"
 #include "sky/engine/tonic/dart_wrappable.h"
 #include "sky/engine/tonic/float64_list.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/ThreadSafeRefCounted.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 
 namespace blink {
@@ -29,14 +28,14 @@ class Paragraph;
 template <>
 struct DartConverter<SkCanvas::VertexMode> : public DartConverterInteger<SkCanvas::VertexMode> {};
 
-class Canvas : public ThreadSafeRefCounted<Canvas>, public DartWrappable {
+class Canvas : public base::RefCountedThreadSafe<Canvas>, public DartWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
-    static PassRefPtr<Canvas> create(PictureRecorder* recorder,
-                                     double left,
-                                     double top,
-                                     double right,
-                                     double bottom);
+    static scoped_refptr<Canvas> create(PictureRecorder* recorder,
+                                        double left,
+                                        double top,
+                                        double right,
+                                        double bottom);
 
     ~Canvas() override;
 
diff --git a/sky/engine/core/painting/CanvasGradient.cpp b/sky/engine/core/painting/CanvasGradient.cpp
index 3aef5805bf8fa8b04de5790cf8b132845f23ad6f..b6a4d14eae893e86d1f0f3f3563400d2ac31b325 100644
--- a/sky/engine/core/painting/CanvasGradient.cpp
+++ b/sky/engine/core/painting/CanvasGradient.cpp
@@ -32,8 +32,8 @@ FOR_EACH_BINDING(DART_REGISTER_NATIVE)
   });
 }
 
-PassRefPtr<CanvasGradient> CanvasGradient::create() {
-  return adoptRef(new CanvasGradient());
+scoped_refptr<CanvasGradient> CanvasGradient::create() {
+  return new CanvasGradient();
 }
 
 void CanvasGradient::initLinear(const std::vector<Point>& end_points,
diff --git a/sky/engine/core/painting/CanvasGradient.h b/sky/engine/core/painting/CanvasGradient.h
index 8ac6c3d6eb4256da456d37cd5bd3a996c7d7add6..fc3619d776f7146cc306b0c590afb40bfb2ad948 100644
--- a/sky/engine/core/painting/CanvasGradient.h
+++ b/sky/engine/core/painting/CanvasGradient.h
@@ -23,7 +23,7 @@ class CanvasGradient : public Shader {
   DEFINE_WRAPPERTYPEINFO();
  public:
   ~CanvasGradient() override;
-  static PassRefPtr<CanvasGradient> create();
+  static scoped_refptr<CanvasGradient> create();
 
   void initLinear(const std::vector<Point>& end_points,
                   const std::vector<CanvasColor>& colors,
diff --git a/sky/engine/core/painting/CanvasImage.h b/sky/engine/core/painting/CanvasImage.h
index b0418500eaf819cf5f68d15eb43cc8e870983195..6a0c1252111873afd631bc1d2b080f40a53257a2 100644
--- a/sky/engine/core/painting/CanvasImage.h
+++ b/sky/engine/core/painting/CanvasImage.h
@@ -5,20 +5,19 @@
 #ifndef SKY_ENGINE_CORE_PAINTING_CANVASIMAGE_H_
 #define SKY_ENGINE_CORE_PAINTING_CANVASIMAGE_H_
 
+#include "base/memory/ref_counted.h"
 #include "sky/engine/tonic/dart_wrappable.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/ThreadSafeRefCounted.h"
 #include "third_party/skia/include/core/SkImage.h"
 
 namespace blink {
 class DartLibraryNatives;
 
-class CanvasImage final : public ThreadSafeRefCounted<CanvasImage>,
+class CanvasImage final : public base::RefCountedThreadSafe<CanvasImage>,
                           public DartWrappable {
   DEFINE_WRAPPERTYPEINFO();
  public:
   ~CanvasImage() override;
-  static PassRefPtr<CanvasImage> create() { return adoptRef(new CanvasImage); }
+  static scoped_refptr<CanvasImage> create() { return new CanvasImage(); }
 
   int width();
   int height();
diff --git a/sky/engine/core/painting/CanvasPath.cpp b/sky/engine/core/painting/CanvasPath.cpp
index 991e3941a26226fb77fd7a6087a610eb5bca933f..fa920648a4ec2fab724938f11be1c4a4ce913859 100644
--- a/sky/engine/core/painting/CanvasPath.cpp
+++ b/sky/engine/core/painting/CanvasPath.cpp
@@ -57,10 +57,10 @@ CanvasPath::~CanvasPath()
 {
 }
 
-PassRefPtr<CanvasPath> CanvasPath::shift(const Offset& offset) {
-  RefPtr<CanvasPath> path = CanvasPath::create();
+scoped_refptr<CanvasPath> CanvasPath::shift(const Offset& offset) {
+  scoped_refptr<CanvasPath> path = CanvasPath::create();
   m_path.offset(offset.sk_size.width(), offset.sk_size.height(), &path->m_path);
-  return path.release();
+  return std::move(path);
 }
 
 } // namespace blink
diff --git a/sky/engine/core/painting/CanvasPath.h b/sky/engine/core/painting/CanvasPath.h
index 510d3c6a66556d54f82117749641835ab548b47b..0008a2d3fc771cdd9398d00f3633352685ae68e7 100644
--- a/sky/engine/core/painting/CanvasPath.h
+++ b/sky/engine/core/painting/CanvasPath.h
@@ -7,13 +7,12 @@
 
 #include "math.h"
 
+#include "base/memory/ref_counted.h"
 #include "sky/engine/core/painting/Offset.h"
 #include "sky/engine/core/painting/Point.h"
 #include "sky/engine/core/painting/RRect.h"
 #include "sky/engine/core/painting/Rect.h"
 #include "sky/engine/tonic/dart_wrappable.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/ThreadSafeRefCounted.h"
 #include "third_party/skia/include/core/SkPath.h"
 
 // Note: There's a very similar class in ../../platform/graphics/Path.h
@@ -25,14 +24,11 @@
 namespace blink {
 class DartLibraryNatives;
 
-class CanvasPath : public ThreadSafeRefCounted<CanvasPath>, public DartWrappable {
+class CanvasPath : public base::RefCountedThreadSafe<CanvasPath>, public DartWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
     ~CanvasPath() override;
-    static PassRefPtr<CanvasPath> create()
-    {
-        return adoptRef(new CanvasPath);
-    }
+    static scoped_refptr<CanvasPath> create() { return new CanvasPath(); }
 
     void moveTo(float x, float y) { m_path.moveTo(x, y); }
     void relativeMoveTo(float x, float y) { m_path.rMoveTo(x, y); }
@@ -68,7 +64,7 @@ public:
 
     const SkPath& path() const { return m_path; }
 
-    PassRefPtr<CanvasPath> shift(const Offset& offset);
+    scoped_refptr<CanvasPath> shift(const Offset& offset);
 
     static void RegisterNatives(DartLibraryNatives* natives);
 
diff --git a/sky/engine/core/painting/ColorFilter.cpp b/sky/engine/core/painting/ColorFilter.cpp
index 6a4baf3088110f324feed80dd178b3116a1b113e..466288789b0b60742c2f596eccceff6c962e0f6d 100644
--- a/sky/engine/core/painting/ColorFilter.cpp
+++ b/sky/engine/core/painting/ColorFilter.cpp
@@ -23,9 +23,9 @@ void ColorFilter::RegisterNatives(DartLibraryNatives* natives) {
   });
 }
 
-PassRefPtr<ColorFilter> ColorFilter::create(CanvasColor color,
-                                            TransferMode transfer_mode) {
-  return adoptRef(new ColorFilter(SkColorFilter::MakeModeFilter(color, transfer_mode)));
+scoped_refptr<ColorFilter> ColorFilter::create(CanvasColor color,
+                                               TransferMode transfer_mode) {
+  return new ColorFilter(SkColorFilter::MakeModeFilter(color, transfer_mode));
 }
 
 ColorFilter::ColorFilter(sk_sp<SkColorFilter> filter)
diff --git a/sky/engine/core/painting/ColorFilter.h b/sky/engine/core/painting/ColorFilter.h
index b974db03166af073a9bc55c7f2ba112ada0c6b00..8acaaf0cce0076eeea6897b807bbe56a4b64afa5 100644
--- a/sky/engine/core/painting/ColorFilter.h
+++ b/sky/engine/core/painting/ColorFilter.h
@@ -5,22 +5,21 @@
 #ifndef SKY_ENGINE_CORE_PAINTING_COLORFILTER_H_
 #define SKY_ENGINE_CORE_PAINTING_COLORFILTER_H_
 
+#include "base/memory/ref_counted.h"
 #include "sky/engine/core/painting/CanvasColor.h"
 #include "sky/engine/core/painting/TransferMode.h"
 #include "sky/engine/tonic/dart_wrappable.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/ThreadSafeRefCounted.h"
 #include "third_party/skia/include/core/SkColorFilter.h"
 
 namespace blink {
 class DartLibraryNatives;
 
-class ColorFilter : public ThreadSafeRefCounted<ColorFilter>, public DartWrappable {
+class ColorFilter : public base::RefCountedThreadSafe<ColorFilter>, public DartWrappable {
   DEFINE_WRAPPERTYPEINFO();
  public:
   ~ColorFilter() override;
-  static PassRefPtr<ColorFilter> create(CanvasColor color,
-                                        TransferMode transfer_mode);
+  static scoped_refptr<ColorFilter> create(CanvasColor color,
+                                           TransferMode transfer_mode);
 
   sk_sp<SkColorFilter> filter() { return filter_; }
 
diff --git a/sky/engine/core/painting/ImageFilter.cpp b/sky/engine/core/painting/ImageFilter.cpp
index e00d578231a7b13b9838d60aaa3c86e4022938da..4c2490aa64a0925805c6ae52f73605beb3de937c 100644
--- a/sky/engine/core/painting/ImageFilter.cpp
+++ b/sky/engine/core/painting/ImageFilter.cpp
@@ -34,8 +34,8 @@ FOR_EACH_BINDING(DART_REGISTER_NATIVE)
   });
 }
 
-PassRefPtr<ImageFilter> ImageFilter::create() {
-  return adoptRef(new ImageFilter());
+scoped_refptr<ImageFilter> ImageFilter::create() {
+  return new ImageFilter();
 }
 
 ImageFilter::ImageFilter() {
diff --git a/sky/engine/core/painting/ImageFilter.h b/sky/engine/core/painting/ImageFilter.h
index 0bee4c96b4c6e517b16fa01dd4e4e826cbfb3923..d2c8d89f9506da9b3350d8eac34eb9646fd0c0cd 100644
--- a/sky/engine/core/painting/ImageFilter.h
+++ b/sky/engine/core/painting/ImageFilter.h
@@ -5,20 +5,19 @@
 #ifndef SKY_ENGINE_CORE_PAINTING_IMAGE_FILTER_H_
 #define SKY_ENGINE_CORE_PAINTING_IMAGE_FILTER_H_
 
+#include "base/memory/ref_counted.h"
 #include "sky/engine/core/painting/CanvasImage.h"
 #include "sky/engine/core/painting/Picture.h"
 #include "sky/engine/tonic/dart_wrappable.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/ThreadSafeRefCounted.h"
 #include "third_party/skia/include/core/SkImageFilter.h"
 
 namespace blink {
 
-class ImageFilter : public ThreadSafeRefCounted<ImageFilter>, public DartWrappable {
+class ImageFilter : public base::RefCountedThreadSafe<ImageFilter>, public DartWrappable {
   DEFINE_WRAPPERTYPEINFO();
  public:
   ~ImageFilter() override;
-  static PassRefPtr<ImageFilter> create();
+  static scoped_refptr<ImageFilter> create();
 
   void initImage(CanvasImage* image);
   void initPicture(Picture*);
diff --git a/sky/engine/core/painting/ImageShader.cpp b/sky/engine/core/painting/ImageShader.cpp
index bc84c57bf3afaa82544c1563d01c03c1dbe51106..9eaf16463cf6c0d776a12fce705d9a69dad3af92 100644
--- a/sky/engine/core/painting/ImageShader.cpp
+++ b/sky/engine/core/painting/ImageShader.cpp
@@ -38,8 +38,8 @@ void ImageShader::RegisterNatives(DartLibraryNatives* natives) {
   });
 }
 
-PassRefPtr<ImageShader> ImageShader::create() {
-  return adoptRef(new ImageShader());
+scoped_refptr<ImageShader> ImageShader::create() {
+  return new ImageShader();
 }
 
 void ImageShader::initWithImage(CanvasImage* image,
diff --git a/sky/engine/core/painting/ImageShader.h b/sky/engine/core/painting/ImageShader.h
index 7eefda7f959362a9c2828138f386a47b3e74ba8a..c49141f8fd5ce71786bd656fa6682dc81eb9b63f 100644
--- a/sky/engine/core/painting/ImageShader.h
+++ b/sky/engine/core/painting/ImageShader.h
@@ -22,7 +22,7 @@ class ImageShader : public Shader {
     DEFINE_WRAPPERTYPEINFO();
  public:
   ~ImageShader() override;
-  static PassRefPtr<ImageShader> create();
+  static scoped_refptr<ImageShader> create();
 
   void initWithImage(CanvasImage* image,
                      SkShader::TileMode tmx,
diff --git a/sky/engine/core/painting/MaskFilter.cpp b/sky/engine/core/painting/MaskFilter.cpp
index d63d6a941f63a2cb354e55bdc0f5b84ab105821d..a7e84507953b8044e0e1f69b5219677d469e8901 100644
--- a/sky/engine/core/painting/MaskFilter.cpp
+++ b/sky/engine/core/painting/MaskFilter.cpp
@@ -24,10 +24,10 @@ void MaskFilter::RegisterNatives(DartLibraryNatives* natives) {
   });
 }
 
-PassRefPtr<MaskFilter> MaskFilter::create(
+scoped_refptr<MaskFilter> MaskFilter::create(
       unsigned style, double sigma, unsigned flags) {
-  return adoptRef(new MaskFilter(SkBlurMaskFilter::Make(
-      static_cast<SkBlurStyle>(style), sigma, flags)));
+  return new MaskFilter(SkBlurMaskFilter::Make(
+      static_cast<SkBlurStyle>(style), sigma, flags));
 }
 
 MaskFilter::MaskFilter(sk_sp<SkMaskFilter> filter)
diff --git a/sky/engine/core/painting/MaskFilter.h b/sky/engine/core/painting/MaskFilter.h
index bf175231784bb0f432230bddb4b64b28a7783479..6bffb04a9352e2e2ab94bc2e766f6cdd9eaba270 100644
--- a/sky/engine/core/painting/MaskFilter.h
+++ b/sky/engine/core/painting/MaskFilter.h
@@ -5,9 +5,8 @@
 #ifndef SKY_ENGINE_CORE_PAINTING_MASKFILTER_H_
 #define SKY_ENGINE_CORE_PAINTING_MASKFILTER_H_
 
+#include "base/memory/ref_counted.h"
 #include "sky/engine/tonic/dart_wrappable.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/ThreadSafeRefCounted.h"
 #include "third_party/skia/include/core/SkMaskFilter.h"
 
 class SkMaskFilter;
@@ -15,11 +14,11 @@ class SkMaskFilter;
 namespace blink {
 class DartLibraryNatives;
 
-class MaskFilter : public ThreadSafeRefCounted<MaskFilter>, public DartWrappable {
+class MaskFilter : public base::RefCountedThreadSafe<MaskFilter>, public DartWrappable {
   DEFINE_WRAPPERTYPEINFO();
  public:
   ~MaskFilter() override;
-  static PassRefPtr<MaskFilter> create(
+  static scoped_refptr<MaskFilter> create(
       unsigned style, double sigma, unsigned flags);
 
   sk_sp<SkMaskFilter> filter() { return filter_; }
diff --git a/sky/engine/core/painting/Picture.cpp b/sky/engine/core/painting/Picture.cpp
index 045d2d5db8c9cb0445364e9fc8859d85771a56aa..ad1fc8111dca8cc0a15b4ffb6b1324f98412f0cd 100644
--- a/sky/engine/core/painting/Picture.cpp
+++ b/sky/engine/core/painting/Picture.cpp
@@ -19,10 +19,10 @@ IMPLEMENT_WRAPPERTYPEINFO(ui, Picture);
 
 DART_BIND_ALL(Picture, FOR_EACH_BINDING)
 
-PassRefPtr<Picture> Picture::create(sk_sp<SkPicture> skPicture)
+scoped_refptr<Picture> Picture::create(sk_sp<SkPicture> skPicture)
 {
     ASSERT(skPicture);
-    return adoptRef(new Picture(skPicture));
+    return new Picture(skPicture);
 }
 
 Picture::Picture(sk_sp<SkPicture> skPicture)
diff --git a/sky/engine/core/painting/Picture.h b/sky/engine/core/painting/Picture.h
index a46cb0ebacb4cf6700590e036ba1b5f0e0f04937..63c4362d05a09c6db737a2bc46744de31c585c4e 100644
--- a/sky/engine/core/painting/Picture.h
+++ b/sky/engine/core/painting/Picture.h
@@ -5,20 +5,19 @@
 #ifndef SKY_ENGINE_CORE_PAINTING_PICTURE_H_
 #define SKY_ENGINE_CORE_PAINTING_PICTURE_H_
 
+#include "base/memory/ref_counted.h"
 #include "sky/engine/tonic/dart_wrappable.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/ThreadSafeRefCounted.h"
 #include "third_party/skia/include/core/SkPicture.h"
 
 namespace blink {
 class Canvas;
 class DartLibraryNatives;
 
-class Picture : public ThreadSafeRefCounted<Picture>, public DartWrappable {
+class Picture : public base::RefCountedThreadSafe<Picture>, public DartWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
     ~Picture() override;
-    static PassRefPtr<Picture> create(sk_sp<SkPicture> skPicture);
+    static scoped_refptr<Picture> create(sk_sp<SkPicture> skPicture);
 
     sk_sp<SkPicture> toSkia() const { return m_picture; }
 
diff --git a/sky/engine/core/painting/PictureRecorder.cpp b/sky/engine/core/painting/PictureRecorder.cpp
index 007a604929c413bce1a54288b7ec473452d40ff6..4da963f3a4711e29133a3230365a0939814921c1 100644
--- a/sky/engine/core/painting/PictureRecorder.cpp
+++ b/sky/engine/core/painting/PictureRecorder.cpp
@@ -50,22 +50,22 @@ SkCanvas* PictureRecorder::beginRecording(SkRect bounds)
         &m_rtreeFactory, SkPictureRecorder::kComputeSaveLayerInfo_RecordFlag);
 }
 
-PassRefPtr<Picture> PictureRecorder::endRecording()
+scoped_refptr<Picture> PictureRecorder::endRecording()
 {
     if (!isRecording())
         return nullptr;
-    RefPtr<Picture> picture = Picture::create(
+    scoped_refptr<Picture> picture = Picture::create(
         m_pictureRecorder.finishRecordingAsPicture());
     m_canvas->clearSkCanvas();
     m_canvas->ClearDartWrapper();
     m_canvas = nullptr;
     ClearDartWrapper();
-    return picture.release();
+    return std::move(picture);
 }
 
-void PictureRecorder::set_canvas(PassRefPtr<Canvas> canvas)
+void PictureRecorder::set_canvas(scoped_refptr<Canvas> canvas)
 {
-    m_canvas = canvas;
+    m_canvas = std::move(canvas);
 }
 
 } // namespace blink
diff --git a/sky/engine/core/painting/PictureRecorder.h b/sky/engine/core/painting/PictureRecorder.h
index 2758eaa1d6b55d165d0dc0a215c080523721637a..1d95e84ceb98b96d62d01cab2c206e75f510aed7 100644
--- a/sky/engine/core/painting/PictureRecorder.h
+++ b/sky/engine/core/painting/PictureRecorder.h
@@ -5,10 +5,9 @@
 #ifndef SKY_ENGINE_CORE_PAINTING_PICTURERECORDER_H_
 #define SKY_ENGINE_CORE_PAINTING_PICTURERECORDER_H_
 
+#include "base/memory/ref_counted.h"
 #include "sky/engine/core/painting/Rect.h"
 #include "sky/engine/tonic/dart_wrappable.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/ThreadSafeRefCounted.h"
 #include "third_party/skia/include/core/SkPictureRecorder.h"
 
 namespace blink {
@@ -16,22 +15,19 @@ class Canvas;
 class DartLibraryNatives;
 class Picture;
 
-class PictureRecorder : public ThreadSafeRefCounted<PictureRecorder>,
+class PictureRecorder : public base::RefCountedThreadSafe<PictureRecorder>,
                         public DartWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
-    static PassRefPtr<PictureRecorder> create()
-    {
-        return adoptRef(new PictureRecorder());
-    }
+    static scoped_refptr<PictureRecorder> create() { return new PictureRecorder(); }
 
     ~PictureRecorder();
 
     SkCanvas* beginRecording(SkRect bounds);
-    PassRefPtr<Picture> endRecording();
+    scoped_refptr<Picture> endRecording();
     bool isRecording();
 
-    void set_canvas(PassRefPtr<Canvas> canvas);
+    void set_canvas(scoped_refptr<Canvas> canvas);
 
     static void RegisterNatives(DartLibraryNatives* natives);
 
@@ -40,7 +36,7 @@ private:
 
     SkRTreeFactory m_rtreeFactory;
     SkPictureRecorder m_pictureRecorder;
-    RefPtr<Canvas> m_canvas;
+    scoped_refptr<Canvas> m_canvas;
 };
 
 } // namespace blink
diff --git a/sky/engine/core/painting/Shader.h b/sky/engine/core/painting/Shader.h
index 450160bd1b1f0097755ac5c0d803a9e65eb738d5..3423d011718797ff8a8b3bfd2cf45c37ff34dd5b 100644
--- a/sky/engine/core/painting/Shader.h
+++ b/sky/engine/core/painting/Shader.h
@@ -5,14 +5,13 @@
 #ifndef SKY_ENGINE_CORE_PAINTING_SHADER_H_
 #define SKY_ENGINE_CORE_PAINTING_SHADER_H_
 
+#include "base/memory/ref_counted.h"
 #include "sky/engine/tonic/dart_wrappable.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/ThreadSafeRefCounted.h"
 #include "third_party/skia/include/core/SkShader.h"
 
 namespace blink {
 
-class Shader : public ThreadSafeRefCounted<Shader>, public DartWrappable {
+class Shader : public base::RefCountedThreadSafe<Shader>, public DartWrappable {
   DEFINE_WRAPPERTYPEINFO();
  public:
   ~Shader() override;
diff --git a/sky/engine/core/painting/painting.cc b/sky/engine/core/painting/painting.cc
index f42b0db5b78af5a5c84a0f39faa074f6b0ef189d..072fca5d9e57adb424e9a3d3e91d6257c65577f3 100644
--- a/sky/engine/core/painting/painting.cc
+++ b/sky/engine/core/painting/painting.cc
@@ -46,7 +46,7 @@ void InvokeImageCallback(sk_sp<SkImage> image,
   if (!image) {
     DartInvoke(callback->value(), {Dart_Null()});
   } else {
-    RefPtr<CanvasImage> resultImage = CanvasImage::create();
+    scoped_refptr<CanvasImage> resultImage = CanvasImage::create();
     resultImage->setImage(std::move(image));
     DartInvoke(callback->value(), {ToDart(resultImage)});
   }
diff --git a/sky/engine/core/text/Paragraph.h b/sky/engine/core/text/Paragraph.h
index 06893e5103e55286c8e028ad64419cd1d0b0a064..a23c221d51e1ae3cf7c228f5da17cdef6e67abdd 100644
--- a/sky/engine/core/text/Paragraph.h
+++ b/sky/engine/core/text/Paragraph.h
@@ -5,9 +5,8 @@
 #ifndef SKY_ENGINE_CORE_TEXT_PARAGRAPH_H_
 #define SKY_ENGINE_CORE_TEXT_PARAGRAPH_H_
 
+#include "base/memory/ref_counted.h"
 #include "sky/engine/tonic/dart_wrappable.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/ThreadSafeRefCounted.h"
 #include "sky/engine/core/painting/Canvas.h"
 #include "sky/engine/core/painting/Offset.h"
 #include "sky/engine/core/rendering/RenderView.h"
@@ -16,11 +15,11 @@
 namespace blink {
 class DartLibraryNatives;
 
-class Paragraph : public ThreadSafeRefCounted<Paragraph>, public DartWrappable {
+class Paragraph : public base::RefCountedThreadSafe<Paragraph>, public DartWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
-    static PassRefPtr<Paragraph> create(PassOwnPtr<RenderView> renderView) {
-      return adoptRef(new Paragraph(renderView));
+    static scoped_refptr<Paragraph> create(PassOwnPtr<RenderView> renderView) {
+      return new Paragraph(renderView);
     }
 
     ~Paragraph() override;
diff --git a/sky/engine/core/text/ParagraphBuilder.cpp b/sky/engine/core/text/ParagraphBuilder.cpp
index 95e275048f8a42feed00959ad196a19c5d7eaa85..e40dd89ed0e07f1c7740008bad79116e4aadd732 100644
--- a/sky/engine/core/text/ParagraphBuilder.cpp
+++ b/sky/engine/core/text/ParagraphBuilder.cpp
@@ -231,7 +231,7 @@ void ParagraphBuilder::addText(const std::string& text)
     m_currentRenderObject->addChild(renderText);
 }
 
-PassRefPtr<Paragraph> ParagraphBuilder::build(Int32List& encoded, const std::string& fontFamily, double fontSize, double lineHeight)
+scoped_refptr<Paragraph> ParagraphBuilder::build(Int32List& encoded, const std::string& fontFamily, double fontSize, double lineHeight)
 {
     DCHECK(encoded.num_elements() == 5);
     int32_t mask = encoded[0];
diff --git a/sky/engine/core/text/ParagraphBuilder.h b/sky/engine/core/text/ParagraphBuilder.h
index 3de56ea6f9ec26ba798c859378d6c7d32c4cd98f..7f2362dad562f78e33c271a44188433b29ac7fc4 100644
--- a/sky/engine/core/text/ParagraphBuilder.h
+++ b/sky/engine/core/text/ParagraphBuilder.h
@@ -8,18 +8,15 @@
 #include "sky/engine/core/text/Paragraph.h"
 #include "sky/engine/tonic/dart_wrappable.h"
 #include "sky/engine/tonic/int32_list.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/ThreadSafeRefCounted.h"
+#include "base/memory/ref_counted.h"
 
 namespace blink {
 class DartLibraryNatives;
 
-class ParagraphBuilder : public ThreadSafeRefCounted<ParagraphBuilder>, public DartWrappable {
+class ParagraphBuilder : public base::RefCountedThreadSafe<ParagraphBuilder>, public DartWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
-    static PassRefPtr<ParagraphBuilder> create() {
-      return adoptRef(new ParagraphBuilder());
-    }
+    static scoped_refptr<ParagraphBuilder> create() { return new ParagraphBuilder(); }
 
     ~ParagraphBuilder() override;
 
@@ -28,7 +25,7 @@ public:
 
     void addText(const std::string& text);
 
-    PassRefPtr<Paragraph> build(Int32List& encoded, const std::string& fontFamily, double fontSize, double lineHeight);
+    scoped_refptr<Paragraph> build(Int32List& encoded, const std::string& fontFamily, double fontSize, double lineHeight);
 
     static void RegisterNatives(DartLibraryNatives* natives);
 
diff --git a/sky/engine/tonic/BUILD.gn b/sky/engine/tonic/BUILD.gn
index 82be21601a98a0948fa23de107f81fc4227da1d3..684b3ba347923c74bfb13553fee896e66dc0ea24 100644
--- a/sky/engine/tonic/BUILD.gn
+++ b/sky/engine/tonic/BUILD.gn
@@ -62,7 +62,6 @@ source_set("tonic") {
     "//dart/runtime/bin:embedded_dart_io",
     "//mojo/data_pipe_utils",
     "//mojo/public/cpp/system",
-    "//sky/engine/wtf",
   ]
 
   public_deps = [
diff --git a/sky/engine/tonic/dart_wrappable.cc b/sky/engine/tonic/dart_wrappable.cc
index 413d60a6baa3fbf15ee9af5c4a9db7e494a62cb3..16c3a2dea04e7787766cdaf60c43fd72242f7c95 100644
--- a/sky/engine/tonic/dart_wrappable.cc
+++ b/sky/engine/tonic/dart_wrappable.cc
@@ -16,9 +16,6 @@ DartWrappable::~DartWrappable() {
   CHECK(!dart_wrapper_);
 }
 
-void DartWrappable::AcceptDartGCVisitor(DartGCVisitor& visitor) const {
-}
-
 Dart_Handle DartWrappable::CreateDartWrapper(DartState* dart_state) {
   DCHECK(!dart_wrapper_);
   const DartWrapperInfo& info = GetDartWrapperInfo();
diff --git a/sky/engine/tonic/dart_wrappable.h b/sky/engine/tonic/dart_wrappable.h
index 8308d51a67b412c1032c5e184fdb3c4f0b2e6f2d..967ee2a66334d60c0912a7c72e5dd12c11710197 100644
--- a/sky/engine/tonic/dart_wrappable.h
+++ b/sky/engine/tonic/dart_wrappable.h
@@ -6,20 +6,17 @@
 #define SKY_ENGINE_TONIC_DART_WRAPPABLE_H_
 
 #include "base/logging.h"
+#include "base/memory/ref_counted.h"
 #include "base/template_util.h"
 #include "dart/runtime/include/dart_api.h"
 #include "sky/engine/tonic/dart_converter.h"
 #include "sky/engine/tonic/dart_error.h"
 #include "sky/engine/tonic/dart_state.h"
 #include "sky/engine/tonic/dart_wrapper_info.h"
-#include "sky/engine/wtf/PassRefPtr.h"
-#include "sky/engine/wtf/RefPtr.h"
-#include "sky/engine/wtf/ThreadSafeRefCounted.h"
 
 #include <type_traits>
 
 namespace blink {
-class DartGCVisitor;
 struct DartWrapperInfo;
 
 // DartWrappable is a base class that you can inherit from in order to be
@@ -39,11 +36,6 @@ class DartWrappable {
   // base class's implementation of this function.
   virtual const DartWrapperInfo& GetDartWrapperInfo() const = 0;
 
-  // Subclasses that wish to integrate with the Dart garbage collector should
-  // override this function. Please call your base class's AcceptDartGCVisitor
-  // at the end of your override.
-  virtual void AcceptDartGCVisitor(DartGCVisitor& visitor) const;
-
   Dart_Handle CreateDartWrapper(DartState* dart_state);
   void AssociateWithDartWrapper(Dart_NativeArguments args);
   void ClearDartWrapper(); // Warning: Might delete this.
@@ -72,10 +64,10 @@ class DartWrappable {
 
 #define IMPLEMENT_WRAPPERTYPEINFO(LibraryName, ClassName)                      \
 static void RefObject_##LibraryName_##ClassName(DartWrappable* impl) {         \
-  static_cast<ClassName*>(impl)->ref();                                        \
+  static_cast<ClassName*>(impl)->AddRef();                                     \
 }                                                                              \
 static void DerefObject_##LibraryName_##ClassName(DartWrappable* impl) {       \
-  static_cast<ClassName*>(impl)->deref();                                      \
+  static_cast<ClassName*>(impl)->Release();                                    \
 }                                                                              \
 static const DartWrapperInfo kDartWrapperInfo_##LibraryName_##ClassName = {    \
   #LibraryName,                                                                \
@@ -86,7 +78,8 @@ static const DartWrapperInfo kDartWrapperInfo_##LibraryName_##ClassName = {    \
 };                                                                             \
 const DartWrapperInfo& ClassName::dart_wrapper_info_ =                         \
     kDartWrapperInfo_##LibraryName_##ClassName;                                \
-static_assert(std::is_base_of<WTF::ThreadSafeRefCountedBase, ClassName>::value,\
+static_assert(std::is_base_of<base::subtle::RefCountedThreadSafeBase,          \
+                              ClassName>::value,                               \
     #ClassName " must be thread-safe reference-countable.");
 
 struct DartConverterWrappable {
@@ -136,20 +129,17 @@ struct DartConverter<
 };
 
 template<typename T>
-struct DartConverter<RefPtr<T>> {
-  static Dart_Handle ToDart(RefPtr<T> val) {
+struct DartConverter<scoped_refptr<T>> {
+  static Dart_Handle ToDart(const scoped_refptr<T>& val) {
     return DartConverter<T*>::ToDart(val.get());
   }
 
-  static RefPtr<T> FromDart(Dart_Handle handle) {
+  static scoped_refptr<T> FromDart(Dart_Handle handle) {
     return DartConverter<T*>::FromDart(handle);
   }
-};
 
-template<typename T>
-struct DartConverter<PassRefPtr<T>> {
   static void SetReturnValue(Dart_NativeArguments args,
-                             PassRefPtr<T> val,
+                             const scoped_refptr<T>& val,
                              bool auto_scope = true) {
     DartConverter<T*>::SetReturnValue(args, val.get());
   }