Add mojo interface+impl for audio stream control.

content/browser/renderer_host/media/audio_output_delegate.h

-// Copyright 2016 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 CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_OUTPUT_DELEGATE_H_
-#define CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_OUTPUT_DELEGATE_H_
-
-#include <memory>
-#include <string>
-
-#include "base/macros.h"
-#include "base/memory/ref_counted.h"
-#include "content/common/content_export.h"
-
-namespace base {
-class SharedMemory;
-class CancelableSyncSocket;
-}
-
-namespace media {
-class AudioOutputController;
-}
-
-namespace content {
-
-class CONTENT_EXPORT AudioOutputDelegate {
- public:
-  class CONTENT_EXPORT EventHandler {
-   public:
-    virtual ~EventHandler() {}
-
-    // All these methods are called on the IO thread.
-
-    // Called when construction is finished and the stream is ready for
-    // playout.
-    virtual void OnStreamCreated(int stream_id,
-                                 base::SharedMemory* shared_memory,
-                                 base::CancelableSyncSocket* socket) = 0;
-
-    // Called if stream encounters an error and has become unusable.
-    virtual void OnStreamError(int stream_id) = 0;
-  };
-
-  virtual ~AudioOutputDelegate() {}
-
-  // TODO(maxmorin): Remove GetController() when crbug.com/647185 is closed.
-  // This function is used to provide control of the audio stream to
-  // WebrtcAudioPrivateGetActiveSinkFunction and others in the webrtc extension
-  // API. Since the controller is shared, this means that it might outlive the
-  // AudioOutputDelegate. In this case, it is still safe to call functions on
-  // the controller, but it will not do anything. The controller is also shared
-  // with AudioStreamMonitor.
-  virtual scoped_refptr<media::AudioOutputController> GetController() const = 0;
-  virtual int GetStreamId() const = 0;
-
-  // Stream control:
-  virtual void OnPlayStream() = 0;
-  virtual void OnPauseStream() = 0;
-  virtual void OnSetVolume(double volume) = 0;
-};
-
-}  // namespace content
-
-#endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_OUTPUT_DELEGATE_H_