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

cc/layer.h

 // Copyright 2010 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_H_
 #define CC_LAYER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 33 matching lines @@
 class ScrollbarLayer;
 struct AnimationEvent;
 struct RenderingStats;
 
 // Base class for composited layers. Special layer types are derived from
 // this class.
 class CC_EXPORT Layer : public base::RefCounted<Layer>,
                         public LayerAnimationValueObserver {
  public:
   typedef std::vector<scoped_refptr<Layer> > LayerList;
+  enum LayerIdLabels {
+    PINCH_ZOOM_ROOT_SCROLL_LAYER_ID = -2,
+    INVALID_ID = -1,
+  };
 
   static scoped_refptr<Layer> Create();
 
   int id() const { return layer_id_; }
 
   Layer* RootLayer();
   Layer* parent() { return parent_; }
   const Layer* parent() const { return parent_; }
   void AddChild(scoped_refptr<Layer> child);
   void InsertChild(scoped_refptr<Layer> child, size_t index);
@@ skipping 24 matching lines @@
 
   void SetMaskLayer(Layer* mask_layer);
   Layer* mask_layer() { return mask_layer_.get(); }
   const Layer* mask_layer() const { return mask_layer_.get(); }
 
   virtual void SetNeedsDisplayRect(const gfx::RectF& dirty_rect);
   void SetNeedsDisplay() { SetNeedsDisplayRect(gfx::RectF(bounds())); }
 
   void SetOpacity(float opacity);
   float opacity() const { return opacity_; }
-  bool OpacityIsAnimating() const;
+  virtual bool OpacityIsAnimating() const;
 
   void SetFilters(const WebKit::WebFilterOperations& filters);
   const WebKit::WebFilterOperations& filters() const { return filters_; }
 
   void SetFilter(const skia::RefPtr<SkImageFilter>& filter);
   skia::RefPtr<SkImageFilter> filter() const { return filter_; }
 
   // Background filters are filters applied to what is behind this layer, when
   // they are viewed through non-opaque regions in this layer. They are used
   // through the WebLayer interface, and are not exposed to HTML.
@@ skipping 365 matching lines @@
   WebKit::WebLayerScrollClient* layer_scroll_client_;
 
   DrawProperties<Layer, RenderSurface> draw_properties_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYER_H_