Have ScriptPromiseResolver on the Oilpan heap always.

Source/core/imagebitmap/ImageBitmapFactories.cpp

 /*
  * Copyright (c) 2013, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 31 matching lines @@
 #include "platform/SharedBuffer.h"
 #include "platform/graphics/BitmapImage.h"
 #include "platform/graphics/ImageSource.h"
 #include "public/platform/WebSize.h"
 #include <v8.h>
 
 namespace blink {
 
 static ScriptPromise fulfillImageBitmap(ScriptState* scriptState, PassRefPtrWillBeRawPtr<ImageBitmap> imageBitmap)
 {
-    RefPtrWillBeRawPtr<ScriptPromiseResolver> resolver = ScriptPromiseResolver::create(scriptState);
+    ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
     ScriptPromise promise = resolver->promise();
     if (imageBitmap) {
         resolver->resolve(imageBitmap);
     } else {
         resolver->reject(ScriptValue(scriptState, v8::Null(scriptState->isolate())));
     }
     return promise;
 }
 
 ScriptPromise ImageBitmapFactories::createImageBitmap(ScriptState* scriptState, EventTarget& eventTarget, Blob* blob, ExceptionState& exceptionState)
@@ skipping 146 matching lines @@
     rejectPromise();
 }
 
 DEFINE_TRACE(ImageBitmapFactories::ImageBitmapLoader)
 {
     visitor->trace(m_factory);
     visitor->trace(m_resolver);
 }
 
 } // namespace blink