Implement pinch-zoom scaling for main-frame scrollbars and pinch-zoom overlay scrollbars.

cc/layer_impl.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 CC_LAYER_IMPL_H_
 #define CC_LAYER_IMPL_H_
 
 #include <string>
 
 #include "base/logging.h"
@@ skipping 198 matching lines @@
     gfx::Vector2d scrollOffset() const { return m_scrollOffset; }
     void setScrollOffset(gfx::Vector2d);
 
     gfx::Vector2d maxScrollOffset() const {return m_maxScrollOffset; }
     void setMaxScrollOffset(gfx::Vector2d);
 
     const gfx::Vector2dF& scrollDelta() const { return m_scrollDelta; }
     void setScrollDelta(const gfx::Vector2dF&);
 
     const gfx::Transform& implTransform() const { return m_implTransform; }
-    void setImplTransform(const gfx::Transform& transform);
+    virtual void setImplTransform(const gfx::Transform& transform);
 
     const gfx::Vector2d& sentScrollDelta() const { return m_sentScrollDelta; }
     void setSentScrollDelta(const gfx::Vector2d& sentScrollDelta);
 
     // Returns the delta of the scroll that was outside of the bounds of the initial scroll
     gfx::Vector2dF scrollBy(const gfx::Vector2dF& scroll);
 
     bool scrollable() const { return m_scrollable; }
     void setScrollable(bool scrollable) { m_scrollable = scrollable; }
 
@@ skipping 180 matching lines @@
     // Group of properties that need to be computed based on the layer tree
     // hierarchy before layers can be drawn.
     DrawProperties<LayerImpl, RenderSurfaceImpl> m_drawProperties;
 
     DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }
 
 #endif  // CC_LAYER_IMPL_H_