[Chromecast] Allow CMA backend to notify of key expiry

chromecast/media/audio/cast_audio_output_stream.cc

 // 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.
 
 #include "chromecast/media/audio/cast_audio_output_stream.h"
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/thread_checker.h"
@@ skipping 157 matching lines @@
   }
 
   void OnEndOfStream(MediaPipelineBackend::Decoder* decoder) override {}
 
   void OnDecoderError(MediaPipelineBackend::Decoder* decoder) override {
     error_ = true;
     if (!completion_cb_.is_null())
       OnPushBufferComplete(decoder_, MediaPipelineBackend::kBufferFailed);
   }
 
+  void OnKeyStatusChanged(const std::string& key_id,
+                          CastKeyStatus key_status,
+                          uint32_t system_code) override {}
+
   base::WeakPtr<CastAudioOutputStream::Backend> GetWeakPtr() {
     return weak_factory_.GetWeakPtr();
   }
 
  private:
   const ::media::AudioParameters audio_params_;
   scoped_ptr<MediaPipelineBackend> backend_;
   scoped_ptr<TaskRunnerImpl> backend_task_runner_;
   MediaPipelineBackend::AudioDecoder* decoder_;
   PushBufferCompletionCallback completion_cb_;
@@ skipping 185 matching lines @@
   audio_task_runner_->PostDelayedTask(
       FROM_HERE,
       base::Bind(&CastAudioOutputStream::PushBuffer,
                  weak_factory_.GetWeakPtr()),
       delay);
   push_in_progress_ = true;
 }
 
 }  // namespace media
 }  // namespace chromecast