chromecast: Cleanup class/struct fwd declarations

chromecast/media/cdm/cast_cdm.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 CHROMECAST_MEDIA_CDM_cast_cdm_H_
 #define CHROMECAST_MEDIA_CDM_cast_cdm_H_
 
 #include <stdint.h>
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/sequenced_task_runner_helpers.h"
 #include "base/threading/thread_checker.h"
 #include "chromecast/media/base/media_resource_tracker.h"
 #include "chromecast/media/cdm/cast_cdm_context.h"
 #include "chromecast/public/media/cast_key_status.h"
 #include "media/base/cdm_context.h"
 #include "media/base/media_keys.h"
 #include "media/base/player_tracker.h"
 #include "media/cdm/json_web_key.h"
 
-namespace base {
-class SingleThreadTaskRunner;
-}
-
 namespace media {
 class PlayerTrackerImpl;
 }
 
 namespace chromecast {
 namespace media {
 class DecryptContextImpl;
 
 // CastCdm is an extension of MediaKeys that provides common
 // functionality across CDM implementations.
@@ skipping 60 matching lines @@
 
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(CastCdm);
 };
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_MEDIA_CDM_cast_cdm_H_