Add rendering context and rendering 2D context to OffscreenCanvas

third_party/WebKit/Source/core/html/canvas/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"
 #include "core/CoreExport.h"
 #include "platform/geometry/IntSize.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
+class CanvasContextCreationAttributes;

[Justin Novosad, 2016/03/02 15:41:50]

The Blink core has no dependency on OffscreenCanvas.  So You should put this in
a new module 'offscreencanvas'

+class OffscreenCanvasRenderingContext;
+class OffscreenCanvasRenderingContextFactory;
+
 class CORE_EXPORT OffscreenCanvas final : public GarbageCollectedFinalized<OffscreenCanvas>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static OffscreenCanvas* create(unsigned width, unsigned height);
 
     IntSize size() const { return m_size; }
     unsigned width() const { return m_size.width(); }
     unsigned height() const { return m_size.height(); }
-
     void setWidth(unsigned);
     void setHeight(unsigned);
 
+    OffscreenCanvasRenderingContext* getContext(const String&, const CanvasContextCreationAttributes&);
+    OffscreenCanvasRenderingContext* renderingContext() const { return m_context.get(); }
+
+    static void registerRenderingContextFactory(PassOwnPtr<OffscreenCanvasRenderingContextFactory>);
+
     DECLARE_VIRTUAL_TRACE();
 
 private:
     OffscreenCanvas(const IntSize&);
 
+    using ContextFactoryVector = Vector<OwnPtr<OffscreenCanvasRenderingContextFactory>>;
+    static ContextFactoryVector& renderingContextFactories();
+    static OffscreenCanvasRenderingContextFactory* getRenderingContextFactory(int);
+
+    OwnPtrWillBeMember<OffscreenCanvasRenderingContext> m_context;
     IntSize m_size;
 };
 
 } // namespace blink
 
 #endif // OffscreenCanvas_h