Reduce texture uploads during scrollbar invalidations.

cc/BitmapCanvasLayerTextureUpdater.h

 // Copyright 2011 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 BitmapCanvasLayerTextureUpdater_h
 #define BitmapCanvasLayerTextureUpdater_h
 
 #if USE(ACCELERATED_COMPOSITING)
 
@@ skipping 26 matching lines @@
     static PassRefPtr<BitmapCanvasLayerTextureUpdater> create(PassOwnPtr<LayerPainterChromium>);
     virtual ~BitmapCanvasLayerTextureUpdater();
 
     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 setOpaque(bool) OVERRIDE;
 
-private:
+protected:
     explicit BitmapCanvasLayerTextureUpdater(PassOwnPtr<LayerPainterChromium>);
 
     OwnPtr<SkCanvas> m_canvas;
     IntSize m_canvasSize;
     bool m_opaque;
 };
 
 } // namespace cc
 #endif // USE(ACCELERATED_COMPOSITING)
 #endif // BitmapCanvasLayerTextureUpdater_h