Remove LayerTreeImpl::SetRootLayerFromLayerListForTesting.

cc/trees/layer_tree_host_common_unittest.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_common.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <memory>
@@ skipping 5213 matching lines @@
 
   child_ptr = root_layer->layer_tree_impl()->LayerById(2);
   tree = root_layer->layer_tree_impl()->property_trees()->effect_tree;
   node = tree.Node(child_ptr->effect_tree_index());
   EXPECT_TRUE(node->data.is_drawn);
   EXPECT_TRUE(tree.ContributesToDrawnSurface(child_ptr->effect_tree_index()));
 
   // But if the opacity of the layer remains 0 after activation, it should not
   // be drawn.
   host_impl.ActivateSyncTree();
-  host_impl.active_tree()->SetRootLayerFromLayerListForTesting();
-  LayerImpl* active_root = host_impl.active_tree()->root_layer_for_testing();
+  LayerImpl* active_root = host_impl.active_tree()->LayerById(root_layer->id());
   LayerImpl* active_child = host_impl.active_tree()->LayerById(child_ptr->id());
 
   EffectTree& active_effect_tree =
       host_impl.active_tree()->property_trees()->effect_tree;
   EXPECT_TRUE(active_effect_tree.needs_update());
 
   ExecuteCalculateDrawProperties(active_root);
 
   node = active_effect_tree.Node(active_child->effect_tree_index());
   EXPECT_FALSE(node->data.is_drawn);
@@ skipping 5148 matching lines @@
   EXPECT_EQ(scroll_child6.id, grand_child10->scroll_tree_index());
   EXPECT_EQ(scroll_root1.id, parent3->scroll_tree_index());
   EXPECT_EQ(scroll_child7.id, child8->scroll_tree_index());
   EXPECT_EQ(scroll_root1.id, parent4->scroll_tree_index());
   EXPECT_EQ(scroll_root1.id, child9->scroll_tree_index());
   EXPECT_EQ(scroll_root1.id, grand_child12->scroll_tree_index());
 }
 
 }  // namespace
 }  // namespace cc