Replace layer id with Element id for tracking scrollbar animation controllers

cc/layers/layer_impl.cc

 // 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.
 
 #include "cc/layers/layer_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 294 matching lines @@
   return LayerImpl::Create(tree_impl, layer_id_);
 }
 
 bool LayerImpl::IsSnapped() {
   return scrollable();
 }
 
 void LayerImpl::PushPropertiesTo(LayerImpl* layer) {
   DCHECK(layer->IsActive());
 
+  // The ElementId should be set first because other setters depend on it such
+  // as LayerImpl::SetScrollClipLayer.
+  layer->SetElementId(element_id_);
+
   layer->offset_to_transform_parent_ = offset_to_transform_parent_;
   layer->main_thread_scrolling_reasons_ = main_thread_scrolling_reasons_;
   layer->user_scrollable_horizontal_ = user_scrollable_horizontal_;
   layer->user_scrollable_vertical_ = user_scrollable_vertical_;
   layer->should_flatten_transform_from_property_tree_ =
       should_flatten_transform_from_property_tree_;
   layer->masks_to_bounds_ = masks_to_bounds_;
   layer->contents_opaque_ = contents_opaque_;
   layer->may_contain_video_ = may_contain_video_;
   layer->use_parent_backface_visibility_ = use_parent_backface_visibility_;
@@ skipping 14 matching lines @@
   layer->scrollbars_hidden_ = scrollbars_hidden_;
   layer->needs_show_scrollbars_ = needs_show_scrollbars_;
 
   if (layer_property_changed_) {
     layer->layer_tree_impl()->set_needs_update_draw_properties();
     layer->layer_property_changed_ = true;
   }
 
   layer->SetBounds(bounds_);
   layer->SetScrollClipLayer(scroll_clip_layer_id_);
-  layer->SetElementId(element_id_);
   layer->SetMutableProperties(mutable_properties_);
 
   // If the main thread commits multiple times before the impl thread actually
   // draws, then damage tracking will become incorrect if we simply clobber the
   // update_rect here. The LayerImpl's update_rect needs to accumulate (i.e.
   // union) any update changes that have occurred on the main thread.
   update_rect_.Union(layer->update_rect());
   layer->SetUpdateRect(update_rect_);
 
   if (owned_debug_info_)
@@ skipping 614 matching lines @@
 
 ScrollTree& LayerImpl::GetScrollTree() const {
   return GetPropertyTrees()->scroll_tree;
 }
 
 TransformTree& LayerImpl::GetTransformTree() const {
   return GetPropertyTrees()->transform_tree;
 }
 
 }  // namespace cc