cc: Clean up root_layer code in LTI

cc/test/test_layer_tree_host_base.cc

Index: cc/test/test_layer_tree_host_base.cc
diff --git a/cc/test/test_layer_tree_host_base.cc b/cc/test/test_layer_tree_host_base.cc
index 214d72523d2d977f737c2730d52b233068d02e04..23aff28c4d2e269f9c926c89ca782c4c4a9aa523 100644
--- a/cc/test/test_layer_tree_host_base.cc
+++ b/cc/test/test_layer_tree_host_base.cc
@@ -105,7 +105,7 @@ void TestLayerTreeHostBase::SetupPendingTree(
       host_impl()->active_tree()->device_scale_factor());
 
   // Steal from the recycled tree if possible.
-  LayerImpl* pending_root = pending_tree->root_layer();
+  LayerImpl* pending_root = pending_tree->root_layer_for_testing();
   std::unique_ptr<FakePictureLayerImpl> pending_layer;
   DCHECK(!pending_root || pending_root->id() == root_id_);
   if (!pending_root) {
@@ -117,7 +117,7 @@ void TestLayerTreeHostBase::SetupPendingTree(
     pending_layer->SetDrawsContent(true);
     pending_layer->SetScrollClipLayer(new_pending_root->id());
     pending_root = new_pending_root.get();
-    pending_tree->SetRootLayer(std::move(new_pending_root));
+    pending_tree->SetRootLayerForTesting(std::move(new_pending_root));
   } else {
     pending_layer.reset(static_cast<FakePictureLayerImpl*>(
         pending_root->test_properties()
@@ -132,9 +132,9 @@ void TestLayerTreeHostBase::SetupPendingTree(
   pending_layer->SetRasterSourceOnPending(raster_source, invalidation);
 
   pending_root->test_properties()->AddChild(std::move(pending_layer));
-  pending_tree->SetViewportLayersFromIds(Layer::INVALID_ID,
-                                         pending_tree->root_layer()->id(),
-                                         Layer::INVALID_ID, Layer::INVALID_ID);
+  pending_tree->SetViewportLayersFromIds(
+      Layer::INVALID_ID, pending_tree->root_layer_for_testing()->id(),
+      Layer::INVALID_ID, Layer::INVALID_ID);
 
   pending_layer_ = static_cast<FakePictureLayerImpl*>(
       host_impl()->pending_tree()->LayerById(id_));