Disable overlay scrollbars in Blink when hidden by the compositor.

cc/layers/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_LAYERS_LAYER_H_
 #define CC_LAYERS_LAYER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 484 matching lines @@
   void ClearPreferredRasterBounds();
 
   AnimationHost* GetAnimationHost() const;
 
   ElementListType GetElementTypeForAnimation() const;
 
   // Tests in remote mode need to explicitly set the layer id so it matches the
   // layer id for the corresponding Layer on the engine.
   void SetLayerIdForTesting(int id);
 
+  void SetScrollbarsHiddenFromImplSide(bool hidden);
+
  protected:
   friend class LayerImpl;
   friend class TreeSynchronizer;
   virtual ~Layer();
   Layer();
 
   LayerTreeHost* layer_tree_host() { return layer_tree_host_; }
 
   // These SetNeeds functions are in order of severity of update:
   //
@@ skipping 221 matching lines @@
   // These all act like draw properties, so don't need push properties.
   gfx::Rect visible_layer_rect_;
   size_t num_unclipped_descendants_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_H_