cc: Clean up root_layer code in LTI

cc/trees/layer_tree_host_unittest_video.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/trees/layer_tree_host.h"
 
 #include "cc/layers/render_surface_impl.h"
 #include "cc/layers/video_layer.h"
 #include "cc/layers/video_layer_impl.h"
 #include "cc/test/fake_video_frame_provider.h"
@@ skipping 29 matching lines @@
   }
 
   void BeginTest() override {
     num_draws_ = 0;
     PostSetNeedsCommitToMainThread();
   }
 
   DrawResult PrepareToDrawOnThread(LayerTreeHostImpl* host_impl,
                                    LayerTreeHostImpl::FrameData* frame,
                                    DrawResult draw_result) override {
-    LayerImpl* root_layer = host_impl->active_tree()->root_layer();
+    LayerImpl* root_layer = host_impl->active_tree()->root_layer_for_testing();
     RenderSurfaceImpl* root_surface = root_layer->render_surface();
     gfx::Rect damage_rect =
         root_surface->damage_tracker()->current_damage_rect();
 
     switch (num_draws_) {
       case 0:
         // First frame the whole viewport is damaged.
         EXPECT_EQ(gfx::Rect(0, 0, 20, 20), damage_rect);
         break;
       case 1:
@@ skipping 25 matching lines @@
   int num_draws_;
   int video_layer_id_;
 
   FakeVideoFrameProvider video_frame_provider_;
 };
 
 SINGLE_AND_MULTI_THREAD_TEST_F(LayerTreeHostVideoTestSetNeedsDisplay);
 
 }  // namespace
 }  // namespace cc