Replace layer id with Element id for tracking scrollbar animation controllers

cc/layers/scrollbar_layer_impl_base.h

 // Copyright 2013 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_BASE_H_
 #define CC_LAYERS_SCROLLBAR_LAYER_IMPL_BASE_H_
 
 #include "base/macros.h"
 #include "cc/cc_export.h"
 #include "cc/input/scrollbar.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/layer_impl.h"
 
 namespace cc {
 
 class LayerTreeImpl;
 
 class CC_EXPORT ScrollbarLayerImplBase : public LayerImpl {
  public:
   int ScrollLayerId() const { return scroll_layer_id_; }
+  ElementId scroll_element_id() const { return scroll_element_id_; }
 
-  void SetScrollLayerId(int scroll_layer_id);
+  void SetScrollInfo(int scroll_layer_id, ElementId scroll_element_id);
 
   float current_pos() const { return current_pos_; }
   bool SetCurrentPos(float current_pos);
   bool SetClipLayerLength(float clip_layer_length);
   bool SetScrollLayerLength(float scroll_layer_length);
   bool SetVerticalAdjust(float vertical_adjust);
 
   float clip_layer_length() const { return clip_layer_length_; }
   float scroll_layer_length() const { return scroll_layer_length_; }
   float vertical_adjust() const { return vertical_adjust_; }
@@ skipping 37 matching lines @@
 
   virtual int ThumbLength() const = 0;
   virtual float TrackLength() const = 0;
   virtual int TrackStart() const = 0;
   // Indicates whether the thumb length can be changed without going back to the
   // main thread.
   virtual bool IsThumbResizable() const = 0;
 
  private:
   int scroll_layer_id_;
+  ElementId scroll_element_id_;
   bool is_overlay_scrollbar_;
 
   float thumb_thickness_scale_factor_;
   float current_pos_;
   float clip_layer_length_;
   float scroll_layer_length_;
   ScrollbarOrientation orientation_;
   bool is_left_side_vertical_scrollbar_;
 
   // Difference between the clip layer's height and the visible viewport
   // height (which may differ in the presence of top-controls hiding).
   float vertical_adjust_;
 
   DISALLOW_COPY_AND_ASSIGN(ScrollbarLayerImplBase);
 };
 
 typedef std::set<ScrollbarLayerImplBase*> ScrollbarSet;
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_SCROLLBAR_LAYER_IMPL_BASE_H_