Note scrollbar layer properties changed when position changes.

cc/layers/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_LAYERS_SCROLLBAR_LAYER_IMPL_H_
 #define CC_LAYERS_SCROLLBAR_LAYER_IMPL_H_
 
 #include "cc/base/cc_export.h"
 #include "cc/input/scrollbar.h"
 #include "cc/layers/layer_impl.h"
@@ skipping 54 matching lines @@
     thumb_resource_id_ = id;
   }
   void set_visible_to_total_length_ratio(float ratio) {
     visible_to_total_length_ratio_ = ratio;
   }
   void set_is_overlay_scrollbar(bool is_overlay_scrollbar) {
     is_overlay_scrollbar_ = is_overlay_scrollbar;
   }
   bool is_overlay_scrollbar() const { return is_overlay_scrollbar_; }
 
-  void SetCurrentPos(float current_pos) { current_pos_ = current_pos; }
-  void SetMaximum(int maximum) { maximum_ = maximum; }
+  void SetCurrentPos(float current_pos);
+  void SetMaximum(int maximum);
 
   gfx::Rect ComputeThumbQuadRect() const;
 
  protected:
   ScrollbarLayerImpl(LayerTreeImpl* tree_impl,
                      int id,
                      ScrollbarOrientation orientation);
 
  private:
   virtual const char* LayerTypeAsString() const OVERRIDE;
@@ skipping 19 matching lines @@
 
   int scroll_layer_id_;
 
   bool is_overlay_scrollbar_;
 
   DISALLOW_COPY_AND_ASSIGN(ScrollbarLayerImpl);
 };
 
 }  // namespace cc
 #endif  // CC_LAYERS_SCROLLBAR_LAYER_IMPL_H_