support video device enumeration from renderer process.

content/renderer/media/media_stream_dispatcher_eventhandler.h

Index: content/renderer/media/media_stream_dispatcher_eventhandler.h
===================================================================
--- content/renderer/media/media_stream_dispatcher_eventhandler.h	(revision 111389)
+++ content/renderer/media/media_stream_dispatcher_eventhandler.h	(working copy)
@@ -33,6 +33,23 @@
   virtual void OnAudioDeviceFailed(const std::string& label,
                                    int index) = 0;
 
+  // A new list of video devices have been enumerated.
+  virtual void OnVideoDevicesEnumerated(
+      int request_id,
+      const media_stream::StreamDeviceInfoArray& device_array) = 0;
+
+  // Failed to enumerate video devices.
+  virtual void OnVideoDevicesEnumerationFailed(int request_id) = 0;
+
+  // A video device has been opened.
+  virtual void OnVideoDeviceOpened(
+      int request_id,
+      const std::string& label,
+      const media_stream::StreamDeviceInfo& video_device) = 0;
+
+  // Failed to open the video device.
+  virtual void OnVideoDeviceOpenFailed(int request_id) = 0;
+
  protected:
   virtual ~MediaStreamDispatcherEventHandler();
 };