Fix cc scrollbar layer issues with initialization, and use element ids throughout.

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 111 matching lines @@
   const Layer* mask_layer() const { return inputs_.mask_layer.get(); }
 
   virtual void SetNeedsDisplayRect(const gfx::Rect& dirty_rect);
   void SetNeedsDisplay() { SetNeedsDisplayRect(gfx::Rect(bounds())); }
 
   virtual void SetOpacity(float opacity);
   float opacity() const { return inputs_.opacity; }
   float EffectiveOpacity() const;
   virtual bool OpacityCanAnimateOnImplThread() const;
 
-  virtual bool AlwaysUseActiveTreeOpacity() const;
-
   void SetBlendMode(SkBlendMode blend_mode);
   SkBlendMode blend_mode() const { return inputs_.blend_mode; }
 
   // A layer is root for an isolated group when it and all its descendants are
   // drawn over a black and fully transparent background, creating an isolated
   // group. It should be used along with SetBlendMode(), in order to restrict
   // layers within the group to blend with layers outside this group.
   void SetIsRootForIsolatedGroup(bool root);
   bool is_root_for_isolated_group() const {
     return inputs_.is_root_for_isolated_group;
@@ skipping 485 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_