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

content/browser/renderer_host/media/audio_input_device_manager_event_handler.h

 // Copyright (c) 2011 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.
 
 // AudioInputDeviceManagerEventHandler is used to signal events from
 // AudioInoutDeviceManager when it's time to start and stop devices.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_INPUT_DEVICE_MANAGER_EVENT_HANDLER_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_INPUT_DEVICE_MANAGER_EVENT_HANDLER_H_
 
 #include "content/common/content_export.h"
 
 namespace media_stream {
 
 class CONTENT_EXPORT AudioInputDeviceManagerEventHandler {
  public:
   // Called by AudioInputDeviceManager to create an audio stream using the
   // device index when the device has been started.
-  virtual void OnDeviceStarted(int session_id, int index) = 0;
+  virtual void OnDeviceStarted(int session_id,
+                               const std::string& device_id) = 0;
 
   // Called by AudioInputDeviceManager to stop the audio stream when a device
   // has been stopped. This method is used only when users call Close() without
   // calling Stop() on a started device.
   virtual void OnDeviceStopped(int session_id) = 0;
 
   virtual ~AudioInputDeviceManagerEventHandler() {}
 };
 
 }  // namespace media_stream
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_INPUT_DEVICE_MANAGER_EVENT_HANDLER_H_