Move ReferencedSurfaceTracker into GpuCompositorFrameSink.

cc/ipc/display_compositor.mojom

Index: cc/ipc/display_compositor.mojom
diff --git a/cc/ipc/display_compositor.mojom b/cc/ipc/display_compositor.mojom
index 1b405f8cd55a7992dcc917e12bb739bae4b68a84..0cc76bf0c4fcdff098bfd3285429301661f8435a 100644
--- a/cc/ipc/display_compositor.mojom
+++ b/cc/ipc/display_compositor.mojom
@@ -61,11 +61,6 @@ interface DisplayCompositor {
 // compositor. The display compositor host is either the browser process in
 // Chrome or the window server process.
 interface DisplayCompositorClient {
-  // Called by the display compostor when it is created. Provides the top level
-  // root surface id that should reference display roots. This will always be
-  // the first message sent.
-  OnDisplayCompositorCreated(cc.mojom.SurfaceId root_surface_id);
-
   // Called by the display compositor immediately upon receiving a
   // CompositorFrame with a new SurfaceId for the first time.
   OnSurfaceCreated(SurfaceInfo surface_info);