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

cc/layers/layer.cc

 // 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.
 
 #include "cc/layers/layer.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 494 matching lines @@
 }
 
 float Layer::EffectiveOpacity() const {
   return inputs_.hide_layer_and_subtree ? 0.f : inputs_.opacity;
 }
 
 bool Layer::OpacityCanAnimateOnImplThread() const {
   return false;
 }
 
-bool Layer::AlwaysUseActiveTreeOpacity() const {
-  return false;
-}
-
 void Layer::SetBlendMode(SkBlendMode blend_mode) {
   DCHECK(IsPropertyChangeAllowed());
   if (inputs_.blend_mode == blend_mode)
     return;
 
   // Allowing only blend modes that are defined in the CSS Compositing standard,
   // plus destination-in which is used to implement masks.
   // http://dev.w3.org/fxtf/compositing-1/#blending
   switch (blend_mode) {
     case SkBlendMode::kSrcOver:
@@ skipping 912 matching lines @@
       ->subtree_has_copy_request;
 }
 
 gfx::Transform Layer::ScreenSpaceTransform() const {
   DCHECK_NE(transform_tree_index_, TransformTree::kInvalidNodeId);
   return draw_property_utils::ScreenSpaceTransform(
       this, layer_tree_host_->property_trees()->transform_tree);
 }
 
 }  // namespace cc