[ozone] Keep the queue of surfaceless buffers inside gl_surface_ozone

ui/ozone/platform/drm/gpu/page_flip_observer.h

Index: ui/ozone/platform/drm/gpu/page_flip_observer.h
diff --git a/ui/ozone/platform/drm/gpu/page_flip_observer.h b/ui/ozone/platform/drm/gpu/page_flip_observer.h
deleted file mode 100644
index f8c066a55c308cc7cd02f24e254adc68e87b8976..0000000000000000000000000000000000000000
--- a/ui/ozone/platform/drm/gpu/page_flip_observer.h
+++ /dev/null
@@ -1,19 +0,0 @@
-// Copyright 2015 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 UI_OZONE_PLATFORM_DRM_GPU_PAGE_FLIP_OBSERVER_H_
-#define UI_OZONE_PLATFORM_DRM_GPU_PAGE_FLIP_OBSERVER_H_
-
-namespace ui {
-
-class PageFlipObserver {
- public:
-  virtual ~PageFlipObserver() {}
-
-  virtual void OnPageFlipEvent() = 0;
-};
-
-}  // namespace ui
-
-#endif  // UI_OZONE_PLATFORM_DRM_GPU_PAGE_FLIP_OBSERVER_H_