cc: Add some tracing below LayerTreeHost::PushProperties.

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index 5489dd44259902fa6a4b4fe9f5697e509485ccec..cb9619b1ebaedd6312310b2a156ae1ffb664ed85 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -382,6 +382,7 @@ void LayerTreeHost::FinishCommitOnImplThread(LayerTreeHostImpl* host_impl) {
     TreeSynchronizer::PushProperties(root_layer(), sync_tree->root_layer());
 
     if (animation_host_) {
+      TRACE_EVENT0("cc", "LayerTreeHost::AnimationHost::PushProperties");
       DCHECK(host_impl->animation_host());
       animation_host_->PushPropertiesTo(host_impl->animation_host());
     }