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

cc/layer_tree_impl.h

Index: cc/layer_tree_impl.h
diff --git a/cc/layer_tree_impl.h b/cc/layer_tree_impl.h
index 6fc4429d9e7752d147f65e639df66901b49a758c..27b438b7ab16e29a5c45107955d3235a0b5e6344 100644
--- a/cc/layer_tree_impl.h
+++ b/cc/layer_tree_impl.h
@@ -17,6 +17,7 @@ class LayerTreeHostImpl;
 class LayerTreeImpl;
 class LayerTreeSettings;
 class OutputSurface;
+class PinchZoomScrollbarsManager;
 class ResourceProvider;
 class TileManager;
 
@@ -62,6 +63,14 @@ class CC_EXPORT LayerTreeImpl {
   HeadsUpDisplayLayerImpl* hud_layer() { return hud_layer_; }
   void set_hud_layer(HeadsUpDisplayLayerImpl* layer_impl) { hud_layer_ = layer_impl; }
 
+  ScrollbarLayerImpl* pinch_zoom_scrollbar_vertical() { return pinch_zoom_scrollbar_vertical_; }
+  void set_pinch_zoom_scrollbar_vertical(ScrollbarLayerImpl* layer_impl);
+
+  ScrollbarLayerImpl* pinch_zoom_scrollbar_horizontal() { return pinch_zoom_scrollbar_horizontal_; }
+  void set_pinch_zoom_scrollbar_horizontal(ScrollbarLayerImpl* layer_impl);
+
+  PinchZoomScrollbarsManager* pinch_zoom_scrollbars_manager() { return pinch_zoom_scrollbars_.get(); }
+
   LayerImpl* root_scroll_layer() { return root_scroll_layer_; }
   void set_root_scroll_layer(LayerImpl* layer_impl) { root_scroll_layer_ = layer_impl; }
 
@@ -77,9 +86,13 @@ protected:
   int source_frame_number_;
   scoped_ptr<LayerImpl> root_layer_;
   HeadsUpDisplayLayerImpl* hud_layer_;
+  ScrollbarLayerImpl* pinch_zoom_scrollbar_vertical_;
+  ScrollbarLayerImpl* pinch_zoom_scrollbar_horizontal_;
   LayerImpl* root_scroll_layer_;
   LayerImpl* currently_scrolling_layer_;
 
+  scoped_ptr<PinchZoomScrollbarsManager> pinch_zoom_scrollbars_;
+
   // Persisted state
   int scrolling_layer_id_from_previous_tree_;