Refactor scroll chaining to use ScrollNodes without going through LayerImpl

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 115 matching lines @@
   return IsActive() ? ElementListType::ACTIVE : ElementListType::PENDING;
 }
 
 void LayerImpl::SetDebugInfo(
     std::unique_ptr<base::trace_event::ConvertableToTraceFormat> debug_info) {
   owned_debug_info_ = std::move(debug_info);
   debug_info_ = owned_debug_info_.get();
   SetNeedsPushProperties();
 }
 
-void LayerImpl::DistributeScroll(ScrollState* scroll_state) {
-  ScrollTree& scroll_tree = GetScrollTree();
-  ScrollNode* scroll_node = scroll_tree.Node(scroll_tree_index());
-  scroll_tree.DistributeScroll(scroll_node, scroll_state);
-}
-
 void LayerImpl::SetTransformTreeIndex(int index) {
   transform_tree_index_ = index;
 }
 
 void LayerImpl::SetClipTreeIndex(int index) {
   clip_tree_index_ = index;
 }
 
 void LayerImpl::SetEffectTreeIndex(int index) {
   effect_tree_index_ = index;
@@ skipping 945 matching lines @@
 
 ScrollTree& LayerImpl::GetScrollTree() const {
   return GetPropertyTrees()->scroll_tree;
 }
 
 TransformTree& LayerImpl::GetTransformTree() const {
   return GetPropertyTrees()->transform_tree;
 }
 
 }  // namespace cc