Renamed ChannelObserver to better describe its purpose

ui/ozone/platform/drm/host/drm_window_host_manager.h

 // Copyright 2014 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_HOST_DRM_WINDOW_HOST_MANAGER_H_
 #define UI_OZONE_PLATFORM_DRM_HOST_DRM_WINDOW_HOST_MANAGER_H_
 
 #include <map>
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/gfx/native_widget_types.h"
 
 namespace gfx {
 class Point;
 }
 
 namespace ui {
 
-class DrmGpuPlatformSupportHost;
 class DrmWindowHost;
 
 // Responsible for keeping the mapping between the allocated widgets and
 // windows.
 class DrmWindowHostManager {
  public:
   DrmWindowHostManager();
   ~DrmWindowHostManager();
 
   gfx::AcceleratedWidget NextAcceleratedWidget();
@@ skipping 33 matching lines @@
   WidgetToWindowMap window_map_;
 
   gfx::AcceleratedWidget event_grabber_ = gfx::kNullAcceleratedWidget;
 
   DISALLOW_COPY_AND_ASSIGN(DrmWindowHostManager);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_DRM_HOST_DRM_WINDOW_HOST_MANAGER_H_