cc: Clean up root_layer code in LTI

cc/test/layer_test_common.cc

Index: cc/test/layer_test_common.cc
diff --git a/cc/test/layer_test_common.cc b/cc/test/layer_test_common.cc
index d5c5a1c9d24314d51fb1baa1f183047b2cf71dae..f5d65a22c7a06df09d6bd9a92e3b55e0e8f5ba6f 100644
--- a/cc/test/layer_test_common.cc
+++ b/cc/test/layer_test_common.cc
@@ -126,8 +126,8 @@ LayerTestCommon::LayerImplTest::LayerImplTest(const LayerTreeSettings& settings)
       layer_impl_id_(2) {
   std::unique_ptr<LayerImpl> root =
       LayerImpl::Create(host_->host_impl()->active_tree(), 1);
-  host_->host_impl()->active_tree()->SetRootLayer(std::move(root));
-  root_layer()->SetHasRenderSurface(true);
+  host_->host_impl()->active_tree()->SetRootLayerForTesting(std::move(root));
+  root_layer_for_testing()->SetHasRenderSurface(true);
   host_->host_impl()->SetVisible(true);
   host_->host_impl()->InitializeRenderer(output_surface_.get());
 
@@ -150,7 +150,7 @@ void LayerTestCommon::LayerImplTest::CalcDrawProps(
     const gfx::Size& viewport_size) {
   LayerImplList layer_list;
   LayerTreeHostCommon::CalcDrawPropsImplInputsForTesting inputs(
-      root_layer(), viewport_size, &layer_list);
+      root_layer_for_testing(), viewport_size, &layer_list);
   LayerTreeHostCommon::CalculateDrawPropertiesForTesting(&inputs);
 }
 
@@ -207,7 +207,7 @@ void LayerTestCommon::LayerImplTest::AppendSurfaceQuadsWithOcclusion(
 void EmptyCopyOutputCallback(std::unique_ptr<CopyOutputResult> result) {}
 
 void LayerTestCommon::LayerImplTest::RequestCopyOfOutput() {
-  root_layer()->test_properties()->copy_requests.push_back(
+  root_layer_for_testing()->test_properties()->copy_requests.push_back(
       CopyOutputRequest::CreateRequest(base::Bind(&EmptyCopyOutputCallback)));
 }