Refactoring Canvas2DLayerBridge to make it easier to write unit tests

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

Index: Source/core/platform/graphics/chromium/Canvas2DLayerBridge.h
diff --git a/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.h b/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.h
index 12f87fa0f0dd9af0e2c5a6eb8c314d46ec4bd97f..7fcd7959dbddc0184a1476de2e114bb34ab45031 100644
--- a/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.h
+++ b/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.h
@@ -51,7 +51,14 @@ public:
         NonOpaque
     };
 
-    static PassOwnPtr<Canvas2DLayerBridge> create(PassRefPtr<GraphicsContext3D>, const IntSize&, OpacityMode);
+    class Helper {
+    public:
+        virtual PassRefPtr<GraphicsContext3D> getContext() = 0;
+        virtual SkSurface* createSurface(GraphicsContext3D*, const IntSize&) = 0;
+        virtual ~Helper() { }
+    };
+
+    static PassOwnPtr<Canvas2DLayerBridge> create(PassOwnPtr<Helper>, const IntSize&, OpacityMode);
 
     virtual ~Canvas2DLayerBridge();
 
@@ -76,23 +83,27 @@ public:
     WebKit::WebLayer* layer();
     void contextAcquired();
     SkCanvas* getCanvas() { return m_canvas; }
+    Helper* helper() { return m_helper.get(); }
 
     unsigned backBufferTexture();
 
     bool isValid();
 
 protected:
-    Canvas2DLayerBridge(PassRefPtr<GraphicsContext3D>, SkDeferredCanvas*, OpacityMode);
+    Canvas2DLayerBridge(PassOwnPtr<Helper>, const IntSize&, OpacityMode, bool* success);
+
     void setRateLimitingEnabled(bool);
 
     SkDeferredCanvas* m_canvas;
     OwnPtr<WebKit::WebExternalTextureLayer> m_layer;
     RefPtr<GraphicsContext3D> m_context;
+    OwnPtr<Helper> m_helper;
     size_t m_bytesAllocated;
     bool m_didRecordDrawCommand;
     bool m_surfaceIsValid;
     int m_framesPending;
     bool m_rateLimitingEnabled;
+    bool m_contentsDrawable;
 
     friend class WTF::DoublyLinkedListNode<Canvas2DLayerBridge>;
     Canvas2DLayerBridge* m_next;