Fixing Canvas2DLayerBridge to handle lost graphics contexts

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 510f479e5cd5dda6bfcee6c7e6c3576f1c0bafec..e7035cb7a436a89e088d3ac4dd801a14e3dfc63b 100644
--- a/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.h
+++ b/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.h
@@ -56,10 +56,8 @@ public:
         Threaded
     };
 
-    static PassOwnPtr<Canvas2DLayerBridge> create(PassRefPtr<GraphicsContext3D> context, SkDeferredCanvas* canvas, OpacityMode opacityMode, ThreadMode threading)
-    {
-        return adoptPtr(new Canvas2DLayerBridge(context, canvas, opacityMode, threading));
-    }
+    static PassOwnPtr<Canvas2DLayerBridge> create(PassRefPtr<GraphicsContext3D>, SkDeferredCanvas*, OpacityMode, ThreadMode);
+    static PassOwnPtr<Canvas2DLayerBridge> create(PassRefPtr<GraphicsContext3D>, const IntSize&, OpacityMode, ThreadMode);
 
     virtual ~Canvas2DLayerBridge();
 
@@ -84,9 +82,12 @@ public:
 
     WebKit::WebLayer* layer();
     void contextAcquired();
+    SkCanvas* getCanvas() {return m_canvas;}
 
     unsigned backBufferTexture();
 
+    bool isValid();
+
 protected:
     Canvas2DLayerBridge(PassRefPtr<GraphicsContext3D>, SkDeferredCanvas*, OpacityMode, ThreadMode);