Renamed ChannelObserver to better describe its purpose

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

 // 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_HOST_DRM_DISPLAY_HOST_H_
 #define UI_OZONE_PLATFORM_DRM_HOST_DRM_DISPLAY_HOST_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/display/types/display_constants.h"
 #include "ui/display/types/native_display_delegate.h"
-#include "ui/ozone/platform/drm/host/channel_observer.h"
+#include "ui/ozone/platform/drm/host/gpu_thread_observer.h"
 
 namespace ui {
 
 struct DisplaySnapshot_Params;
 class DisplaySnapshot;
 class DrmGpuPlatformSupportHost;
 
-class DrmDisplayHost : public ChannelObserver {
+class DrmDisplayHost : public GpuThreadObserver {
  public:
   DrmDisplayHost(DrmGpuPlatformSupportHost* sender,
                  const DisplaySnapshot_Params& params,
                  bool is_dummy);
   ~DrmDisplayHost() override;
 
   DisplaySnapshot* snapshot() const { return snapshot_.get(); }
 
   void UpdateDisplaySnapshot(const DisplaySnapshot_Params& params);
   void Configure(const DisplayMode* mode,
                  const gfx::Point& origin,
                  const ConfigureCallback& callback);
   void GetHDCPState(const GetHDCPStateCallback& callback);
   void SetHDCPState(HDCPState state, const SetHDCPStateCallback& callback);
   void SetGammaRamp(const std::vector<GammaRampRGBEntry>& lut);
 
   // Called when the IPC from the GPU process arrives to answer the above
   // commands.
   void OnDisplayConfigured(bool status);
   void OnHDCPStateReceived(bool status, HDCPState state);
   void OnHDCPStateUpdated(bool status);
 
-  // ChannelObserver:
-  void OnChannelEstablished() override;
-  void OnChannelDestroyed() override;
+  // GpuThreadObserver:
+  void OnGpuThreadReady() override;
+  void OnGpuThreadRetired() override;
 
  private:
   // Calls all the callbacks with failure.
   void ClearCallbacks();
 
   DrmGpuPlatformSupportHost* sender_;  // Not owned.
 
   scoped_ptr<DisplaySnapshot> snapshot_;
 
   // Used during startup to signify that any display configuration should be
   // synchronous and succeed.
   bool is_dummy_;
 
   ConfigureCallback configure_callback_;
   GetHDCPStateCallback get_hdcp_callback_;
   SetHDCPStateCallback set_hdcp_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(DrmDisplayHost);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_DRM_HOST_DRM_DISPLAY_HOST_H_