Throw exception for null listener in addEventListener

We appear to be missing a null check here as well.

R=ojan@chromium.org, esprehn@chromium.org

Review URL: https://codereview.chromium.org/937443002

engine/bindings/dart_event_listener.cc

@@ -8,6 +8,7 @@
 #include "sky/engine/core/events/Event.h"
 #include "sky/engine/tonic/dart_api_scope.h"
 #include "sky/engine/tonic/dart_error.h"
+#include "sky/engine/tonic/dart_exception_factory.h"
 #include "sky/engine/tonic/dart_gc_visitor.h"
 #include "sky/engine/tonic/dart_isolate_scope.h"
 
@@ -66,4 +67,18 @@ void DartEventListener::Finalize(void* isolate_callback_data,
   listener->deref();  // Balances ref in DartEventListener::DartEventListener
 }
 
+PassRefPtr<EventListener>
+DartConverter<EventListener*>::FromArgumentsWithNullCheck(
+    Dart_NativeArguments args,
+    int index,
+    Dart_Handle& exception) {
+  Dart_Handle handle = Dart_GetNativeArgument(args, index);
+  if (Dart_IsNull(handle)) {
+    DartState* state = DartState::Current();
+    exception = state->exception_factory().CreateNullArgumentException(index);
+    return nullptr;
+  }
+  return FromDart(handle);
+}
+
 }  // namespace blink

engine/bindings/dart_event_listener.h

@@ -51,12 +51,7 @@ struct DartConverter<EventListener*> {
   static PassRefPtr<EventListener> FromArgumentsWithNullCheck(
       Dart_NativeArguments args,
       int index,
-      Dart_Handle& exception) {
-    Dart_Handle handle = Dart_GetNativeArgument(args, index);
-    if (Dart_IsNull(handle))
-      return nullptr;
-    return FromDart(handle);
-  }
+      Dart_Handle& exception);
 };
 
 }  // namespace blink

engine/tonic/dart_exception_factory.cc

@@ -7,6 +7,7 @@
 
 #include "sky/engine/tonic/dart_converter.h"
 #include "sky/engine/tonic/dart_builtin.h"
+#include "sky/engine/wtf/text/StringBuilder.h"
 
 namespace blink {
 
@@ -17,6 +18,14 @@ DartExceptionFactory::DartExceptionFactory(DartState* dart_state)
 DartExceptionFactory::~DartExceptionFactory() {
 }
 
+Dart_Handle DartExceptionFactory::CreateNullArgumentException(int index) {
+  StringBuilder message;
+  message.appendLiteral("Argument ");
+  message.appendNumber(index);
+  message.appendLiteral(" cannot be null.");
+  return CreateException("ArgumentError", message.toString());
+}
+
 Dart_Handle DartExceptionFactory::CreateException(const String& class_name,
                                                   const String& message) {
   if (core_library_.is_empty()) {

engine/tonic/dart_exception_factory.h

@@ -17,6 +17,7 @@ class DartExceptionFactory {
   explicit DartExceptionFactory(DartState* dart_state);
   ~DartExceptionFactory();
 
+  Dart_Handle CreateNullArgumentException(int index);
   Dart_Handle CreateException(const String& class_name, const String& message);
 
  private:

engine/tonic/dart_wrappable.cc

@@ -10,7 +10,6 @@
 #include "sky/engine/tonic/dart_exception_factory.h"
 #include "sky/engine/tonic/dart_state.h"
 #include "sky/engine/tonic/dart_wrapper_info.h"
-#include "sky/engine/wtf/text/StringBuilder.h"
 
 namespace blink {
 
@@ -79,12 +78,7 @@ DartWrappable* DartConverterWrappable::FromArgumentsWithNullCheck(
   Dart_Handle handle = Dart_GetNativeArgument(args, index);
   if (Dart_IsNull(handle)) {
     DartState* state = DartState::Current();
-    StringBuilder message;
-    message.appendLiteral("Argument ");
-    message.appendNumber(index);
-    message.appendLiteral(" cannot be null.");
-    exception = state->exception_factory().CreateException("ArgumentError",
-                                                           message.toString());
+    exception = state->exception_factory().CreateNullArgumentException(index);
     return nullptr;
   }
   intptr_t native_fields[DartWrappable::kNumberOfNativeFields];