support video device enumeration from renderer process.

content/browser/renderer_host/media/media_stream_device_settings.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.
 
 // MediaStreamDeviceSettings is used to decide which of the available capture
 // device to use as well as getting user permission to use the capture device.
 // There will be one instance of MediaStreamDeviceSettings handling all
 // requests.
 
 // This version always accepts the first device in the list(s), but this will
@@ skipping 33 matching lines @@
   explicit MediaStreamDeviceSettings(SettingsRequester* requester);
   ~MediaStreamDeviceSettings();
 
   // Called when a new request of capture device usage is made.
   void RequestCaptureDeviceUsage(const std::string& label,
                                  int render_process_id,
                                  int render_view_id,
                                  const StreamOptions& stream_components,
                                  const std::string& security_origin);
 
-  // Called as response to SettingsRequester::GetDevices. One response for each
-  // call to |GetDevices| is expected.
+  // Called to pass in an array of available devices for a request represented
+  // by |label|. There could be multiple calls for a request.
   void AvailableDevices(const std::string& label, MediaStreamType stream_type,
                         const StreamDeviceInfoArray& devices);
 
   // Used for testing only. This function is called to use faked UI, which is
   // needed for server based tests. The first non-opened device(s) will be
   // picked.
   void UseFakeUI();
 
  private:
   struct SettingsRequest;
 
   SettingsRequester* requester_;
 
   typedef std::map<std::string, SettingsRequest*> SettingsRequests;
   SettingsRequests requests_;
 
   bool use_fake_ui_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaStreamDeviceSettings);
 };
 
 }  // namespace media_stream
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_STREAM_DEVICE_SETTINGS_H_