Reland of: Make OffscreenCanvas Transferable

third_party/WebKit/Source/bindings/core/v8/Transferables.h

 // Copyright 2016 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.
 
 #ifndef Transferables_h
 #define Transferables_h
 
 #include "core/CoreExport.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Noncopyable.h"
 
 namespace blink {
 
 class DOMArrayBufferBase;
 class ImageBitmap;
+class OffscreenCanvas;
 class MessagePort;
 
 using ArrayBufferArray = HeapVector<Member<DOMArrayBufferBase>>;
 using ImageBitmapArray = HeapVector<Member<ImageBitmap>>;
+using OffscreenCanvasArray = HeapVector<Member<OffscreenCanvas>>;
 using MessagePortArray = HeapVector<Member<MessagePort>>;
 
 class CORE_EXPORT Transferables final {
     STACK_ALLOCATED();
     WTF_MAKE_NONCOPYABLE(Transferables);
 public:
     Transferables()
     {
     }
 
     ArrayBufferArray arrayBuffers;
     ImageBitmapArray imageBitmaps;
+    OffscreenCanvasArray offscreenCanvases;
     MessagePortArray messagePorts;
 };
 
 // Along with extending |Transferables| to hold a new kind of transferable
 // objects, serialization handling code changes are required:
 //   - extend ScriptValueSerializer::copyTransferables()
 //   - alter SerializedScriptValue(Factory) to do the actual transfer.
 
 } // namespace blink
 
 #endif // Transferables_h