Remove LayerTreeImpl::SetRootLayerFromLayerListForTesting.

cc/trees/layer_tree_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_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 255 matching lines @@
     RemoveLayer(root_layer_for_testing_->id());
   root_layer_for_testing_ = layer.get();
   ClearLayerList();
   if (layer) {
     AddLayer(std::move(layer));
     BuildLayerListForTesting();
   }
   layer_tree_host_impl_->OnCanDrawStateChangedForTree();
 }
 
-void LayerTreeImpl::SetRootLayerFromLayerListForTesting() {
-  root_layer_for_testing_ = layer_list_.empty() ? nullptr : layer_list_[0];
-}
-
 void LayerTreeImpl::OnCanDrawStateChangedForTree() {
   layer_tree_host_impl_->OnCanDrawStateChangedForTree();
 }
 
 void LayerTreeImpl::AddToLayerList(LayerImpl* layer) {
   layer_list_.push_back(layer);
 }
 
 void LayerTreeImpl::ClearLayerList() {
   layer_list_.clear();
@@ skipping 1807 matching lines @@
 
 void LayerTreeImpl::ResetAllChangeTracking() {
   layers_that_should_push_properties_.clear();
   // Iterate over all layers, including masks and replicas.
   for (auto& layer : *layers_)
     layer->ResetChangeTracking();
   property_trees_.ResetAllChangeTracking();
 }
 
 }  // namespace cc