Refactor delegated scrolling in LayerImpl

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 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/trees/layer_tree_host_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 
@@ skipping 2743 matching lines @@
 
 void LayerTreeHostImpl::SetRootLayerScrollOffsetDelegate(
       LayerScrollOffsetDelegate* root_layer_scroll_offset_delegate) {
   root_layer_scroll_offset_delegate_ = root_layer_scroll_offset_delegate;
   active_tree_->SetRootLayerScrollOffsetDelegate(
       root_layer_scroll_offset_delegate_);
 }
 
 void LayerTreeHostImpl::OnRootLayerDelegatedScrollOffsetChanged() {
   DCHECK(root_layer_scroll_offset_delegate_);
+  active_tree_->DistributeRootScrollOffset();
   client_->SetNeedsCommitOnImplThread();
   SetNeedsRedraw();
-  active_tree_->OnRootLayerDelegatedScrollOffsetChanged();
   active_tree_->set_needs_update_draw_properties();
 }
 
 void LayerTreeHostImpl::ClearCurrentlyScrollingLayer() {
   active_tree_->ClearCurrentlyScrollingLayer();
   did_lock_scrolling_layer_ = false;
   scroll_affects_scroll_handler_ = false;
   accumulated_root_overscroll_ = gfx::Vector2dF();
 }
 
@@ skipping 653 matching lines @@
   new_target.SetToMin(layer_impl->MaxScrollOffset());
 
   curve->UpdateTarget(
       animation->TrimTimeToCurrentIteration(CurrentBeginFrameArgs().frame_time)
           .InSecondsF(),
       new_target);
 
   return true;
 }
 }  // namespace cc