Web setting for canvas2d msaa

Source/core/platform/graphics/chromium/Canvas2DLayerBridge.h

 /*
  * Copyright (C) 2012 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
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 };
 
 class Canvas2DLayerBridge : public WebKit::WebExternalTextureLayerClient, public SkDeferredCanvas::NotificationClient, public DoublyLinkedListNode<Canvas2DLayerBridge>, public RefCounted<Canvas2DLayerBridge> {
     WTF_MAKE_NONCOPYABLE(Canvas2DLayerBridge);
 public:
     enum OpacityMode {
         Opaque,
         NonOpaque
     };
 
-    static PassRefPtr<Canvas2DLayerBridge> create(PassRefPtr<GraphicsContext3D>, const IntSize&, OpacityMode);
+    static PassRefPtr<Canvas2DLayerBridge> create(PassRefPtr<GraphicsContext3D>, const IntSize&, OpacityMode, int msaaSampleCount);
 
     virtual ~Canvas2DLayerBridge();
 
     // WebKit::WebExternalTextureLayerClient implementation.
     virtual WebKit::WebGraphicsContext3D* context() OVERRIDE;
     virtual bool prepareMailbox(WebKit::WebExternalTextureMailbox*, WebKit::WebExternalBitmap*) OVERRIDE;
     virtual void mailboxReleased(const WebKit::WebExternalTextureMailbox&) OVERRIDE;
 
     // SkDeferredCanvas::NotificationClient implementation
     virtual void prepareForDraw() OVERRIDE;
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         MailboxInfo(const MailboxInfo&);
         MailboxInfo() {}
     };
     MailboxInfo* createMailboxInfo();
 
     uint32_t m_lastImageId;
     Vector<MailboxInfo> m_mailboxes;
 };
 }
 #endif