diff --git a/sky/services/vsync/BUILD.gn b/sky/services/vsync/BUILD.gn
index 8b9e4200181a515d97a607562d77bcfb759db82e..c5caf8e5826127f5a67719f72277e5cf6d36e36d 100644
--- a/sky/services/vsync/BUILD.gn
+++ b/sky/services/vsync/BUILD.gn
@@ -27,7 +27,7 @@ if (is_android) {
   import("//build/config/android/rules.gni")
 
   android_library("vsync_lib") {
-    java_files = [ "src/org/domokit/vsync/VsyncProviderImpl.java" ]
+    java_files = [ "src/org/domokit/vsync/VSyncProviderImpl.java" ]
 
     deps = [
       "//base:base_java",
diff --git a/sky/services/vsync/src/org/domokit/vsync/VSyncProviderImpl.java b/sky/services/vsync/src/org/domokit/vsync/VSyncProviderImpl.java
new file mode 100644
index 0000000000000000000000000000000000000000..3087cd1405886c60769b4ad1b9394371715b4161
--- /dev/null
+++ b/sky/services/vsync/src/org/domokit/vsync/VSyncProviderImpl.java
@@ -0,0 +1,47 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.domokit.vsync;
+
+import android.view.Choreographer;
+
+import org.chromium.mojo.system.MessagePipeHandle;
+import org.chromium.mojo.system.MojoException;
+import org.chromium.mojom.vsync.VSyncProvider;
+
+/**
+ * Android implementation of VSyncProvider.
+ */
+public class VSyncProviderImpl implements VSyncProvider, Choreographer.FrameCallback {
+    private Choreographer mChoreographer;
+    private AwaitVSyncResponse mCallback;
+    private MessagePipeHandle mPipe;
+
+    public VSyncProviderImpl(MessagePipeHandle pipe) {
+        mPipe = pipe;
+        mChoreographer = Choreographer.getInstance();
+    }
+
+    @Override
+    public void close() {}
+
+    @Override
+    public void onConnectionError(MojoException e) {}
+
+    @Override
+    public void awaitVSync(final AwaitVSyncResponse callback) {
+        if (mCallback != null) {
+            mPipe.close();
+            return;
+        }
+        mCallback = callback;
+        mChoreographer.postFrameCallback(this);
+    }
+
+    @Override
+    public void doFrame(long frameTimeNanos) {
+        mCallback.call(frameTimeNanos / 1000);
+        mCallback = null;
+    }
+}
diff --git a/sky/services/vsync/src/org/domokit/vsync/VsyncProviderImpl.java b/sky/services/vsync/src/org/domokit/vsync/VsyncProviderImpl.java
deleted file mode 100644
index fa0d6d28bfd0fac32b3b5d04e5ddea5587a8f1bf..0000000000000000000000000000000000000000
--- a/sky/services/vsync/src/org/domokit/vsync/VsyncProviderImpl.java
+++ /dev/null
@@ -1,36 +0,0 @@
-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-package org.domokit.vsync;
-
-import android.view.Choreographer;
-
-import org.chromium.mojo.system.MojoException;
-import org.chromium.mojom.vsync.VsyncProvider;
-
-/**
- * Android implementation of VsyncProvider.
- */
-public class VsyncProviderImpl implements VsyncProvider {
-    private static final String TAG = "VsyncProviderImpl";
-
-    public VsyncProviderImpl() {
-    }
-
-    @Override
-    public void close() {}
-
-    @Override
-    public void onConnectionError(MojoException e) {}
-
-    @Override
-    public void awaitVsync(final AwaitVsyncResponse callback) {
-        Choreographer.getInstance().postFrameCallback(new Choreographer.FrameCallback() {
-            @Override
-            public void doFrame(long frameTimeNanos) {
-                callback.call(frameTimeNanos);
-            }
-        });
-    }
-}
diff --git a/sky/services/vsync/vsync.mojom b/sky/services/vsync/vsync.mojom
index d4445bac749013878e21bf6b215d3f0563904f84..715b9067994ab9b8069270ff719a25e738348f6c 100644
--- a/sky/services/vsync/vsync.mojom
+++ b/sky/services/vsync/vsync.mojom
@@ -4,6 +4,8 @@
 
 module vsync;
 
-interface VsyncProvider {
-  AwaitVsync() => (int64 time_stamp);
+interface VSyncProvider {
+  // Timebase is in MojoGetTimeTicksNow.
+  // Only one callback can be parked at a given time.
+  AwaitVSync() => (int64 time_stamp);
 };
diff --git a/sky/shell/android/org/domokit/sky/shell/SkyApplication.java b/sky/shell/android/org/domokit/sky/shell/SkyApplication.java
index f89fae83102982b357f02002f5f1a91abd48ab50..ca27b1637302601b4cad22b10e0d764270294b94 100644
--- a/sky/shell/android/org/domokit/sky/shell/SkyApplication.java
+++ b/sky/shell/android/org/domokit/sky/shell/SkyApplication.java
@@ -21,11 +21,11 @@ import org.chromium.mojom.keyboard.KeyboardService;
 import org.chromium.mojom.media.MediaService;
 import org.chromium.mojom.mojo.NetworkService;
 import org.chromium.mojom.sensors.SensorService;
-import org.chromium.mojom.vsync.VsyncProvider;
+import org.chromium.mojom.vsync.VSyncProvider;
 import org.domokit.activity.ActivityImpl;
 import org.domokit.media.MediaServiceImpl;
 import org.domokit.oknet.NetworkServiceImpl;
-import org.domokit.vsync.VsyncProviderImpl;
+import org.domokit.vsync.VSyncProviderImpl;
 
 /**
  * Sky implementation of {@link android.app.Application}, managing application-level global
@@ -100,10 +100,10 @@ public class SkyApplication extends BaseChromiumApplication {
             }
         });
 
-        registry.register(VsyncProvider.MANAGER.getName(), new ServiceFactory() {
+        registry.register(VSyncProvider.MANAGER.getName(), new ServiceFactory() {
             @Override
             public void connectToService(Context context, Core core, MessagePipeHandle pipe) {
-                VsyncProvider.MANAGER.bind(new VsyncProviderImpl(), pipe);
+                VSyncProvider.MANAGER.bind(new VSyncProviderImpl(pipe), pipe);
             }
         });
     }
diff --git a/sky/shell/ui/animator.cc b/sky/shell/ui/animator.cc
index 39eb5cf3124884a3571e4e395f90f599f4b0328c..990d9b108339d10ef6bb14dc2b903a4a9e159602 100644
--- a/sky/shell/ui/animator.cc
+++ b/sky/shell/ui/animator.cc
@@ -11,7 +11,7 @@
 namespace sky {
 namespace shell {
 
-const int kPipelineDepth = 2;
+const int kPipelineDepth = 3;
 
 Animator::Animator(const Engine::Config& config, Engine* engine)
     : config_(config),
@@ -39,10 +39,7 @@ void Animator::RequestFrame() {
     return;
   }
 
-  if (vsync_provider_) {
-    vsync_provider_->AwaitVsync(
-        base::Bind(&Animator::BeginFrame, weak_factory_.GetWeakPtr()));
-  } else {
+  if (!AwaitVSync()) {
     base::MessageLoop::current()->PostTask(
         FROM_HERE,
         base::Bind(&Animator::BeginFrame, weak_factory_.GetWeakPtr(), 0));
@@ -87,9 +84,19 @@ void Animator::OnFrameComplete() {
 
   if (did_defer_frame_request_) {
     did_defer_frame_request_ = false;
-    BeginFrame(0);
+
+    if (!AwaitVSync())
+      BeginFrame(0);
   }
 }
 
+bool Animator::AwaitVSync() {
+  if (!vsync_provider_)
+    return false;
+  vsync_provider_->AwaitVSync(
+      base::Bind(&Animator::BeginFrame, weak_factory_.GetWeakPtr()));
+  return true;
+}
+
 }  // namespace shell
 }  // namespace sky
diff --git a/sky/shell/ui/animator.h b/sky/shell/ui/animator.h
index 764b3b01079a2b2bb7cb3fa9dba0217bf1464cbd..1befdad15d8e6dbbee78986c2234b7c2ebceaa2e 100644
--- a/sky/shell/ui/animator.h
+++ b/sky/shell/ui/animator.h
@@ -22,17 +22,18 @@ class Animator {
   void Start();
   void Stop();
 
-  void set_vsync_provider(vsync::VsyncProviderPtr vsync_provider) {
+  void set_vsync_provider(vsync::VSyncProviderPtr vsync_provider) {
     vsync_provider_ = vsync_provider.Pass();
   }
 
  private:
   void BeginFrame(int64_t time_stamp);
   void OnFrameComplete();
+  bool AwaitVSync();
 
   Engine::Config config_;
   Engine* engine_;
-  vsync::VsyncProviderPtr vsync_provider_;
+  vsync::VSyncProviderPtr vsync_provider_;
   int outstanding_requests_;
   bool did_defer_frame_request_;
   bool engine_requested_frame_;
diff --git a/sky/shell/ui/engine.cc b/sky/shell/ui/engine.cc
index 840dd9fa0205c7fa7ae4b8000d09f6f48ea14fe9..5fdef5eb7bd93c284ec777a660cfec1ebdf3088e 100644
--- a/sky/shell/ui/engine.cc
+++ b/sky/shell/ui/engine.cc
@@ -67,8 +67,8 @@ Engine::Engine(const Config& config)
   mojo::ConnectToService(service_provider.get(), &network_service_);
 
 #if defined(OS_ANDROID)
-  // TODO(abarth): Implement VsyncProvider on other platforms.
-  vsync::VsyncProviderPtr vsync_provider;
+  // TODO(abarth): Implement VSyncProvider on other platforms.
+  vsync::VSyncProviderPtr vsync_provider;
   mojo::ConnectToService(service_provider.get(), &vsync_provider);
   animator_->set_vsync_provider(vsync_provider.Pass());
 #endif