Add viewport scrollbar class to support overlay scrollbars for pinch zoom virtual viewport.

cc/trees/layer_tree_host.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_TREES_LAYER_TREE_HOST_H_
 #define CC_TREES_LAYER_TREE_HOST_H_
 
 #include <limits>
 #include <vector>
 
@@ skipping 161 matching lines @@
   void SetNeedsRedrawRect(gfx::Rect damage_rect);
   bool CommitRequested() const;
 
   void SetAnimationEvents(scoped_ptr<AnimationEventsVector> events,
                           base::Time wall_clock_time);
 
   void SetRootLayer(scoped_refptr<Layer> root_layer);
   Layer* root_layer() { return root_layer_.get(); }
   const Layer* root_layer() const { return root_layer_.get(); }
 
+  void RegisterPinchViewportLayers(
+      scoped_refptr<Layer> inner_viewport_clip_layer,
+      scoped_refptr<Layer> page_scale_layer,
+      scoped_refptr<Layer> inner_viewport_scroll_layer,
+      scoped_refptr<Layer> outer_viewport_scroll_layer,
+      scoped_refptr<Layer> inner_viewport_horizontal_scrollbar_layer,
+      scoped_refptr<Layer> inner_viewport_vertical_scrollbar_layer);
+
   const LayerTreeSettings& settings() const { return settings_; }
 
   void SetDebugState(const LayerTreeDebugState& debug_state);
   const LayerTreeDebugState& debug_state() const { return debug_state_; }
 
   void SetViewportSize(gfx::Size device_viewport_size);
   void SetOverdrawBottomHeight(float overdraw_bottom_height);
 
   gfx::Size device_viewport_size() const { return device_viewport_size_; }
   float overdraw_bottom_height() const { return overdraw_bottom_height_; }
@@ skipping 104 matching lines @@
   scoped_ptr<Proxy> proxy_;
 
   int commit_number_;
   scoped_ptr<RenderingStatsInstrumentation> rendering_stats_instrumentation_;
 
   bool output_surface_can_be_initialized_;
   bool output_surface_lost_;
   int num_failed_recreate_attempts_;
 
   scoped_refptr<Layer> root_layer_;
+  scoped_refptr<Layer> inner_viewport_clip_layer_;
+  scoped_refptr<Layer> page_scale_layer_;
+  scoped_refptr<Layer> inner_viewport_scroll_layer_;
+  scoped_refptr<Layer> outer_viewport_scroll_layer_;
+  scoped_refptr<Layer> inner_viewport_horizontal_scrollbar_layer_;
+  scoped_refptr<Layer> inner_viewport_vertical_scrollbar_layer_;
   scoped_refptr<HeadsUpDisplayLayer> hud_layer_;
 
   scoped_ptr<PrioritizedResourceManager> contents_texture_manager_;
   scoped_ptr<PrioritizedResource> surface_memory_placeholder_;
 
   base::WeakPtr<InputHandler> input_handler_weak_ptr_;
   base::WeakPtr<TopControlsManager> top_controls_manager_weak_ptr_;
 
   LayerTreeSettings settings_;
   LayerTreeDebugState debug_state_;
@@ skipping 48 matching lines @@
     int64 total_num_cc_layers_will_use_lcd_text;
   };
   LCDTextMetrics lcd_text_metrics_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHost);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_H_