Reland of: Make OffscreenCanvas Transferable

third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.h

 // 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.
 
 #ifndef OffscreenCanvas_h
 #define OffscreenCanvas_h
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "bindings/core/v8/ScriptWrappable.h"
@@ skipping 14 matching lines @@
     // IDL attributes
     unsigned width() const { return m_size.width(); }
     unsigned height() const { return m_size.height(); }
     void setWidth(unsigned);
     void setHeight(unsigned);
 
     // API Methods
     ImageBitmap* transferToImageBitmap(ExceptionState&);
 
     IntSize size() const { return m_size; }
-    void setAssociatedCanvas(HTMLCanvasElement* canvas) { m_canvas = canvas; }
-    HTMLCanvasElement* getAssociatedCanvas() const { return m_canvas; }
+    void setAssociatedCanvasId(int canvasId) { m_canvasId = canvasId; }

[Justin Novosad, 2016/04/26 20:08:32]

I do not see any tests that verify that transfered OffscreenCanvas objects
correctly carry over their associated CanvasId.  Should you a unit test for
that, I think.

[xidachen, 2016/04/26 20:40:59]

Per offline discussion: this ID will be verified once we have the commit() flow
works.

+    int getAssociatedCanvasId() const { return m_canvasId; }
+    bool isNeutered() const { return m_isNeutered; }
+    void setNeutered();
     CanvasRenderingContext* getCanvasRenderingContext(const String&, const CanvasContextCreationAttributes&);
+    CanvasRenderingContext* renderingContext() { return m_context.get(); }
 
     static void registerRenderingContextFactory(PassOwnPtr<CanvasRenderingContextFactory>);
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     explicit OffscreenCanvas(const IntSize&);
 
     using ContextFactoryVector = Vector<OwnPtr<CanvasRenderingContextFactory>>;
     static ContextFactoryVector& renderingContextFactories();
     static CanvasRenderingContextFactory* getRenderingContextFactory(int);
 
     Member<CanvasRenderingContext> m_context;
-    WeakMember<HTMLCanvasElement> m_canvas;
+    int m_canvasId = -1; // DOMNodeIds starts from 0, using -1 to indicate no associated canvas element.
     IntSize m_size;
+    bool m_isNeutered = false;
 };
 
 } // namespace blink
 
 #endif // OffscreenCanvas_h