Add Mojo API for Blink hit testing

ui/aura/local/layer_tree_frame_sink_local.cc

Index: ui/aura/local/layer_tree_frame_sink_local.cc
diff --git a/ui/aura/local/layer_tree_frame_sink_local.cc b/ui/aura/local/layer_tree_frame_sink_local.cc
index 2583d0677c17b7c88555beddadbfe1ac0031a341..4e6708a8f8865e5675fb31f1ab5d3eb7b23da442 100644
--- a/ui/aura/local/layer_tree_frame_sink_local.cc
+++ b/ui/aura/local/layer_tree_frame_sink_local.cc
@@ -33,7 +33,7 @@ bool LayerTreeFrameSinkLocal::BindToClient(
   thread_checker_ = base::MakeUnique<base::ThreadChecker>();
 
   support_ = host_frame_sink_manager_->CreateCompositorFrameSinkSupport(
-      this, frame_sink_id_, false /* is_root */,
+      this, nullptr, frame_sink_id_, false /* is_root */,
       true /* handles_frame_sink_id_invalidation */,
       true /* needs_sync_points */);
   begin_frame_source_ = base::MakeUnique<viz::ExternalBeginFrameSource>(this);