cc: Merge LayerTree into the LayerTreeHost.

cc/test/layer_tree_pixel_test.cc

Index: cc/test/layer_tree_pixel_test.cc
diff --git a/cc/test/layer_tree_pixel_test.cc b/cc/test/layer_tree_pixel_test.cc
index 6b5ff6a367ae44a1e488822744faad8af12a017b..b59c54d0b29cac5aaee2a6e3c8789b01bb367131 100644
--- a/cc/test/layer_tree_pixel_test.cc
+++ b/cc/test/layer_tree_pixel_test.cc
@@ -102,7 +102,7 @@ void LayerTreePixelTest::ReadbackResult(
 
 void LayerTreePixelTest::BeginTest() {
   Layer* target =
-      readback_target_ ? readback_target_ : layer_tree()->root_layer();
+      readback_target_ ? readback_target_ : layer_tree_host()->root_layer();
   target->RequestCopyOfOutput(CreateCopyOutputRequest());
   PostSetNeedsCommitToMainThread();
 }
@@ -215,7 +215,7 @@ void LayerTreePixelTest::SetupTree() {
   scoped_refptr<Layer> root = Layer::Create();
   root->SetBounds(content_root_->bounds());
   root->AddChild(content_root_);
-  layer_tree()->SetRootLayer(root);
+  layer_tree_host()->SetRootLayer(root);
   LayerTreeTest::SetupTree();
 }