Add/remove surface references via MojoCompositorFrameSink.

services/ui/surfaces/display_compositor.cc

Index: services/ui/surfaces/display_compositor.cc
diff --git a/services/ui/surfaces/display_compositor.cc b/services/ui/surfaces/display_compositor.cc
index 9f466291fe5a395fa60257343eea6a8baa5e852d..16d9010a76ff694817c9bf0bf25c81512a80ea7f 100644
--- a/services/ui/surfaces/display_compositor.cc
+++ b/services/ui/surfaces/display_compositor.cc
@@ -28,6 +28,8 @@ DisplayCompositor::DisplayCompositor(
       reference_manager_(&manager_),
       binding_(this, std::move(request)) {
   manager_.AddObserver(this);
+  if (client_)
+    client_->OnRootSurfaceId(GetRootSurfaceId());
 }
 
 void DisplayCompositor::CreateCompositorFrameSink(
@@ -54,14 +56,11 @@ void DisplayCompositor::CreateCompositorFrameSink(
           std::move(private_request), std::move(client));
 }
 
-void DisplayCompositor::AddRootSurfaceReference(const cc::SurfaceId& child_id) {
+void DisplayCompositor::AddSurfaceReference(const cc::SurfaceReference& ref) {
   DCHECK(thread_checker_.CalledOnValidThread());
-  AddSurfaceReference(GetRootSurfaceId(), child_id);
-}
+  const cc::SurfaceId& parent_id = ref.parent_id();
+  const cc::SurfaceId& child_id = ref.child_id();
 
-void DisplayCompositor::AddSurfaceReference(const cc::SurfaceId& parent_id,
-                                            const cc::SurfaceId& child_id) {
-  DCHECK(thread_checker_.CalledOnValidThread());
   auto vector_iter = temp_references_.find(child_id.frame_sink_id());
 
   // If there are no temporary references for the FrameSinkId then we can just
@@ -110,18 +109,11 @@ void DisplayCompositor::AddSurfaceReference(const cc::SurfaceId& parent_id,
     refs.erase(refs.begin(), ++temp_ref_iter);
 }
 
-void DisplayCompositor::RemoveRootSurfaceReference(
-    const cc::SurfaceId& child_id) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  RemoveSurfaceReference(GetRootSurfaceId(), child_id);
-}
-
-void DisplayCompositor::RemoveSurfaceReference(const cc::SurfaceId& parent_id,
-                                               const cc::SurfaceId& child_id) {
-  DCHECK(thread_checker_.CalledOnValidThread());
+void DisplayCompositor::RemoveSurfaceReference(
+    const cc::SurfaceReference& ref) {
   // TODO(kylechar): Each remove reference can trigger GC, it would be better if
   // we GC only once if removing multiple references.
-  reference_manager_->RemoveSurfaceReference(parent_id, child_id);
+  reference_manager_->RemoveSurfaceReference(ref.parent_id(), ref.child_id());
 }
 
 DisplayCompositor::~DisplayCompositor() {