Add IPC interface for switching the audio output device for a given audio stream in the browser.

media/audio/audio_output_ipc.h

 // Copyright (c) 2012 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 MEDIA_AUDIO_AUDIO_OUTPUT_IPC_H_
 #define MEDIA_AUDIO_AUDIO_OUTPUT_IPC_H_
 
+#include <string>
+
 #include "base/memory/shared_memory.h"
 #include "base/sync_socket.h"
 #include "media/audio/audio_parameters.h"
 #include "media/base/media_export.h"
+#include "url/gurl.h"
 
 namespace media {
 
 // Contains IPC notifications for the state of the server side
 // (AudioOutputController) audio state changes and when an AudioOutputController
 // has been created.  Implemented by AudioOutputDevice.
 class MEDIA_EXPORT AudioOutputIPCDelegate {
  public:
   // Current status of the audio output stream in the browser process. Browser
   // sends information about the current playback state and error to the
   // renderer process using this type.
   enum State {
     kPlaying,
     kPaused,
     kError,
     kStateLast = kError
   };
 
+  // Result of an audio output device switch operation
+  enum SwitchOutputDeviceResult {
+    kSuccess = 0,
+    kNotFoundError,
+    kSecurityError,
+    kObsoleteError,
+    kNotSupportedError,
+    kOtherError,

[miu, 2015/06/09 19:49:25]

The naming "kOtherError" is vague; and, if you go with my suggestion in ARH, it
isn't actually being used for anything.  So, I suggest removing it.

[Guido Urdaneta, 2015/06/10 09:44:55]

Done. 
The idea was to use kOtherError for other (no pun intended) errors in the next
CL. Will initially use other values instead in those cases, and see how the
review goes.

+    kSwitchOutputDeviceResultLast = kOtherError
+  };
+
   // Called when state of an audio stream has changed.
   virtual void OnStateChanged(State state) = 0;
 
   // Called when an audio stream has been created.
   // The shared memory |handle| points to a memory section that's used to
   // transfer audio buffers from the AudioOutputIPCDelegate back to the
   // AudioRendererHost.  The implementation of OnStreamCreated takes ownership.
   // The |socket_handle| is used by AudioRendererHost to signal requests for
   // audio data to be written into the shared memory. The AudioOutputIPCDelegate
   // must read from this socket and provide audio whenever data (search for
@@ skipping 42 matching lines @@
   // AudioOutputController in the peer process.
   virtual void CloseStream() = 0;
 
   // Sets the volume of the audio stream.
   virtual void SetVolume(double volume) = 0;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_IPC_H_