Oilpan: keep ImageData on the heap by default.

Source/platform/heap/Handle.h

 /*
  * Copyright (C) 2014 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 825 matching lines @@
     private:
 
 #define DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(type) \
     type::~type() { }
 
 #define DEFINE_STATIC_REF_WILL_BE_PERSISTENT(type, name, arguments) \
     DEFINE_STATIC_REF(type, name, arguments)
 
 #endif // ENABLE(OILPAN)
 
+// Abstraction for injecting calls to an object's 'dispose()' method
+// on leaving a stack scope, ensuring earlier release of resources
+// than waiting until the object is eventually GCed.
+template<typename T>
+class ScopedDisposal {
+    STACK_ALLOCATED();
+public:
+    ScopedDisposal(T* object)
+        : m_object(object)
+    {
+        static_assert(IsGarbageCollectedType<T>::value, "can only be used with garbage collected types");
+    }
+
+    ~ScopedDisposal()
+    {
+        if (m_object)
+            m_object->dispose();
+    }
+
+    void clear() { m_object.clear(); }
+
+private:
+    Member<T> m_object;
+};
+
 } // namespace blink
 
 namespace WTF {
 
 template <typename T> struct VectorTraits<blink::Member<T>> : VectorTraitsBase<blink::Member<T>> {
     static const bool needsDestruction = false;
     static const bool canInitializeWithMemset = true;
     static const bool canMoveWithMemcpy = true;
 };
 
@@ skipping 178 matching lines @@
 template<typename T>
 struct ParamStorageTraits<RawPtr<T>> : public PointerParamStorageTraits<T*, blink::IsGarbageCollectedType<T>::value> {
 };
 
 template<typename T>
 PassRefPtr<T> adoptRef(blink::RefCountedGarbageCollected<T>*) = delete;
 
 } // namespace WTF
 
 #endif