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

cc/scrollbar_layer_impl.h

 // Copyright 2012 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_SCROLLBAR_LAYER_IMPL_H_
 #define CC_SCROLLBAR_LAYER_IMPL_H_
 
 #include "cc/cc_export.h"
 #include "cc/scrollbar_geometry_fixed_thumb.h"
 #include "cc/scrollbar_layer_impl_base.h"
@@ skipping 21 matching lines @@
 
   void set_back_track_resource_id(ResourceProvider::ResourceId id) {
     back_track_resource_id_ = id;
   }
   void set_fore_track_resource_id(ResourceProvider::ResourceId id) {
     fore_track_resource_id_ = id;
   }
   void set_thumb_resource_id(ResourceProvider::ResourceId id) {
     thumb_resource_id_ = id;
   }
+  bool HasThumbTexture() { return thumb_resource_id_; }
 
 
   // ScrollbarLayerImplBase implementation.
   virtual float CurrentPos() const OVERRIDE;
   virtual int TotalSize() const OVERRIDE;
   virtual int Maximum() const OVERRIDE;
 
   void SetCurrentPos(float current_pos) { current_pos_ = current_pos; }
   void SetTotalSize(int total_size) { total_size_ = total_size; }
   void SetMaximum(int maximum) { maximum_ = maximum; }
@@ skipping 73 matching lines @@
 
   bool is_scrollable_area_active_;
   bool is_scroll_view_scrollbar_;
   bool enabled_;
   bool is_custom_scrollbar_;
   bool is_overlay_scrollbar_;
 };
 
 }
 #endif  // CC_SCROLLBAR_LAYER_IMPL_H_