Remove SurfaceReferenceManager interface.

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 4c3e0685f2fa20cfbbbe68fd90e5929863e79429..c00278af363d00e05554b59d8f251e092e531dd5 100644
--- a/services/ui/surfaces/display_compositor.cc
+++ b/services/ui/surfaces/display_compositor.cc
@@ -34,7 +34,6 @@ DisplayCompositor::DisplayCompositor(
     cc::mojom::DisplayCompositorRequest request,
     cc::mojom::DisplayCompositorClientPtr client)
     : manager_(cc::SurfaceManager::LifetimeType::REFERENCES),
-      reference_manager_(&manager_),
       gpu_service_(std::move(gpu_service)),
       gpu_memory_buffer_manager_(std::move(gpu_memory_buffer_manager)),
       image_factory_(image_factory),
@@ -149,10 +148,6 @@ std::unique_ptr<cc::Display> DisplayCompositor::CreateDisplay(
       base::MakeUnique<cc::TextureMailboxDeleter>(task_runner_.get()));
 }
 
-const cc::SurfaceId& DisplayCompositor::GetRootSurfaceId() const {
-  return reference_manager_->GetRootSurfaceId();
-}
-
 void DisplayCompositor::OnSurfaceCreated(const cc::SurfaceInfo& surface_info) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK_GT(surface_info.device_scale_factor(), 0.0f);