Delete dead (and obsolete) display compositor API

services/ui/gpu/display_compositor/compositor_frame_sink_delegate.h

-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef SERVICES_UI_GPU_DISPLAY_COMPOSITOR_COMPOSITOR_FRAME_SINK_DELEGATE_H_
-#define SERVICES_UI_GPU_DISPLAY_COMPOSITOR_COMPOSITOR_FRAME_SINK_DELEGATE_H_
-
-#include "cc/surfaces/surface_id.h"
-
-namespace ui {
-namespace gpu {
-
-class CompositorFrameSinkImpl;
-
-// A CompositorFrameSinkDelegate decouples CompositorFrameSinks from their
-// factories enabling them to be unit tested.
-class CompositorFrameSinkDelegate {
- public:
-  virtual void CompositorFrameSinkConnectionLost(int sink_id) = 0;
-
-  virtual cc::SurfaceId GenerateSurfaceId() = 0;
-};
-
-}  // namespace gpu
-}  // namespace ui
-
-#endif  // SERVICES_UI_GPU_DISPLAY_COMPOSITOR_COMPOSITOR_FRAME_SINK_DELEGATE_H_