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

media/audio/audio_output_ipc.h

Index: media/audio/audio_output_ipc.h
diff --git a/media/audio/audio_output_ipc.h b/media/audio/audio_output_ipc.h
index f85d8e0195325dfc3add33238bc77d56a9d85cc2..05032525e6ce1f32e2c8259bc4cf52354765eba9 100644
--- a/media/audio/audio_output_ipc.h
+++ b/media/audio/audio_output_ipc.h
@@ -5,10 +5,13 @@
 #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 {
 
@@ -27,6 +30,16 @@ class MEDIA_EXPORT AudioOutputIPCDelegate {
     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;