Reduce texture uploads during scrollbar invalidations.

cc/BitmapCanvasLayerTextureUpdater.h

Index: cc/BitmapCanvasLayerTextureUpdater.h
diff --git a/cc/BitmapCanvasLayerTextureUpdater.h b/cc/BitmapCanvasLayerTextureUpdater.h
index f975310d80164ce3349354d57c59298b46c0a8b6..6a16da4e06b178ce93f52280be276b47dd5c42f8 100644
--- a/cc/BitmapCanvasLayerTextureUpdater.h
+++ b/cc/BitmapCanvasLayerTextureUpdater.h
@@ -40,11 +40,11 @@ public:
     virtual PassOwnPtr<LayerTextureUpdater::Texture> createTexture(CCPrioritizedTextureManager*) OVERRIDE;
     virtual SampledTexelFormat sampledTexelFormat(GC3Denum textureFormat) OVERRIDE;
     virtual void prepareToUpdate(const IntRect& contentRect, const IntSize& tileSize, float contentsWidthScale, float contentsHeightScale, IntRect& resultingOpaqueRect, CCRenderingStats&) OVERRIDE;
-    void updateTextureRect(CCResourceProvider*, CCPrioritizedTexture*, const IntRect& sourceRect, const IntSize& destOffset);
+    virtual void updateTextureRect(CCResourceProvider*, CCPrioritizedTexture*, const IntRect& sourceRect, const IntSize& destOffset);
 
     virtual void setOpaque(bool) OVERRIDE;
 
-private:
+protected:
     explicit BitmapCanvasLayerTextureUpdater(PassOwnPtr<LayerPainterChromium>);
 
     OwnPtr<SkCanvas> m_canvas;