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

content/common/media/audio_messages.h

Index: content/common/media/audio_messages.h
diff --git a/content/common/media/audio_messages.h b/content/common/media/audio_messages.h
index 57dd4a66b67945af617f71968b2c925ca4f86b92..14958bb7c5589338d877fc2a03d43223a1bc669e 100644
--- a/content/common/media/audio_messages.h
+++ b/content/common/media/audio_messages.h
@@ -5,6 +5,8 @@
 // IPC messages for the audio.
 // Multiply-included message file, hence no include guard.
 
+#include <string>
+
 #include "base/basictypes.h"
 #include "base/memory/shared_memory.h"
 #include "base/sync_socket.h"
@@ -14,6 +16,7 @@
 #include "media/audio/audio_input_ipc.h"
 #include "media/audio/audio_output_ipc.h"
 #include "media/audio/audio_parameters.h"
+#include "url/gurl.h"
 
 #undef IPC_MESSAGE_EXPORT
 #define IPC_MESSAGE_EXPORT CONTENT_EXPORT
@@ -25,6 +28,10 @@ IPC_ENUM_TRAITS_MAX_VALUE(media::AudioInputIPCDelegate::State,
 IPC_ENUM_TRAITS_MAX_VALUE(media::AudioOutputIPCDelegate::State,
                           media::AudioOutputIPCDelegate::kStateLast)
 
+IPC_ENUM_TRAITS_MAX_VALUE(
+    media::AudioOutputIPCDelegate::SwitchOutputDeviceResult,
+    media::AudioOutputIPCDelegate::kSwitchOutputDeviceResultLast)
+
 IPC_STRUCT_BEGIN(AudioInputHostMsg_CreateStream_Config)
   IPC_STRUCT_MEMBER(media::AudioParameters, params)
   IPC_STRUCT_MEMBER(bool, automatic_gain_control)
@@ -71,6 +78,14 @@ IPC_MESSAGE_CONTROL2(AudioInputMsg_NotifyStreamVolume,
                      int /* stream id */,
                      double /* volume */)
 
+// Notification message sent from AudioRendererHost to renderer for state
+// update after the renderer has requested a SwitchOutputDevice.
+IPC_MESSAGE_CONTROL3(
+    AudioMsg_NotifyOutputDeviceSwitched,
+    int /* stream id */,
+    int /* request id */,
+    media::AudioOutputIPCDelegate::SwitchOutputDeviceResult /* result */)
+
 // Messages sent from the renderer to the browser.
 
 // Request that is sent to the browser for creating an audio output stream.
@@ -121,3 +136,11 @@ IPC_MESSAGE_CONTROL2(AudioHostMsg_SetVolume,
 IPC_MESSAGE_CONTROL2(AudioInputHostMsg_SetVolume,
                      int /* stream_id */,
                      double /* volume */)
+
+// Switch the output device of the stream specified by stream_id.
+IPC_MESSAGE_CONTROL5(AudioHostMsg_SwitchOutputDevice,
+                     int /* stream_id */,
+                     int /* render_frame_id */,
+                     std::string /* device_id */,
+                     GURL /* security_origin */,
+                     int /* request_id */)