Link things together and enable the device selection for linux and mac.

content/renderer/media/audio_input_message_filter.h

Index: content/renderer/media/audio_input_message_filter.h
diff --git a/content/renderer/media/audio_input_message_filter.h b/content/renderer/media/audio_input_message_filter.h
index 89fdd54933f71cf2f3310cdd3239dc36e4eda6ac..43f38d8ddfa218664a674d15dcbf5d51b5af35ff 100644
--- a/content/renderer/media/audio_input_message_filter.h
+++ b/content/renderer/media/audio_input_message_filter.h
@@ -39,7 +39,7 @@ class AudioInputMessageFilter : public IPC::ChannelProxy::MessageFilter {
 
     // Called when the device referenced by the index has been started in
     // the browswer process.
-    virtual void OnDeviceReady(int index) = 0;
+    virtual void OnDeviceReady(const std::string& device_id) = 0;
 
    protected:
     virtual ~Delegate() {}
@@ -82,7 +82,7 @@ class AudioInputMessageFilter : public IPC::ChannelProxy::MessageFilter {
   void OnStreamStateChanged(int stream_id, AudioStreamState state);
 
   // Notification of the opened device of an audio session.
-  void OnDeviceStarted(int stream_id, int index);
+  void OnDeviceStarted(int stream_id, const std::string& device_id);
 
   // A map of stream ids to delegates.
   IDMap<Delegate> delegates_;