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,
+    kSwitchOutputDeviceResultLast = kNotSupportedError

[ncarter (slow), 2015/06/10 18:10:48]

"Though the Google C++ Style Guide now says to use kConstantNaming for enums,
Chromium was written using MACRO_STYLE naming.  Continue to use this style for
consistency." -- https://www.chromium.org/developers/coding-style

[ncarter (slow), 2015/06/10 18:13:03]

Also: "enum values should start with the name of the type, i.e.
PAGE_TRANSITION_LINK in the content::PageTransition enum" -- 
http://www.chromium.org/developers/content-module/content-api

[Guido Urdaneta, 2015/06/10 18:23:05]

I'm using kStyle here because the file contains a previously existing enum
(State) written using kStyle, so I applied the principle of consistency with
existing code. Should I
1. Rewrite both enums in MACRO_STYLE? (would involve other files unrelated to
this CL)
2. Leave both enums in kStyle? (and perhaps add a TODO to rewrite)
3. Rewrite SwitchOutputDeviceResult, but not State?

[ncarter (slow), 2015/06/10 19:14:20]

Tell you what: if you do 3, I'll send you a patch to rewrite State.

In content there are 31 kStyle enums and 328 MACRO_STYLE enums.

[Guido Urdaneta, 2015/06/11 00:51:57]

Done.

+  };
+
   // 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_