Move ReferencedSurfaceTracker into GpuCompositorFrameSink.

components/exo/compositor_frame_sink.cc

Index: components/exo/compositor_frame_sink.cc
diff --git a/components/exo/compositor_frame_sink.cc b/components/exo/compositor_frame_sink.cc
index 3418413efcc57b591c3842b93535ab09eb448d13..c49758a40667eb45d6afb09dccdbd76803fbb5ef 100644
--- a/components/exo/compositor_frame_sink.cc
+++ b/components/exo/compositor_frame_sink.cc
@@ -36,18 +36,6 @@ void CompositorFrameSink::SubmitCompositorFrame(
   support_.SubmitCompositorFrame(local_frame_id, std::move(frame));
 }
 
-void CompositorFrameSink::AddSurfaceReferences(
-    const std::vector<cc::SurfaceReference>& references) {
-  // TODO(fsamuel, staraz): Implement this.
-  NOTIMPLEMENTED();
-}
-
-void CompositorFrameSink::RemoveSurfaceReferences(
-    const std::vector<cc::SurfaceReference>& references) {
-  // TODO(fsamuel, staraz): Implement this.
-  NOTIMPLEMENTED();
-}
-
 void CompositorFrameSink::EvictFrame() {
   support_.EvictFrame();
 }