Move FrameSink hierarchy registration to DisplayCompositor interface

components/display_compositor/gpu_root_compositor_frame_sink.cc

Index: components/display_compositor/gpu_root_compositor_frame_sink.cc
diff --git a/components/display_compositor/gpu_root_compositor_frame_sink.cc b/components/display_compositor/gpu_root_compositor_frame_sink.cc
index 4254c6b9f0a70601efc1e8a4e1de0f6020eac00b..76180bab6dd8ca86e57765abf5c2e5a4c0b6863e 100644
--- a/components/display_compositor/gpu_root_compositor_frame_sink.cc
+++ b/components/display_compositor/gpu_root_compositor_frame_sink.cc
@@ -99,16 +99,6 @@ void GpuRootCompositorFrameSink::Satisfy(const cc::SurfaceSequence& sequence) {
   support_->Satisfy(sequence);
 }
 
-void GpuRootCompositorFrameSink::AddChildFrameSink(
-    const cc::FrameSinkId& child_frame_sink_id) {
-  support_->AddChildFrameSink(child_frame_sink_id);
-}
-
-void GpuRootCompositorFrameSink::RemoveChildFrameSink(
-    const cc::FrameSinkId& child_frame_sink_id) {
-  support_->RemoveChildFrameSink(child_frame_sink_id);
-}
-
 void GpuRootCompositorFrameSink::RequestCopyOfSurface(
     std::unique_ptr<cc::CopyOutputRequest> request) {
   support_->RequestCopyOfSurface(std::move(request));