support video device enumeration from renderer process.

content/browser/renderer_host/media/media_stream_requester.h

Index: content/browser/renderer_host/media/media_stream_requester.h
===================================================================
--- content/browser/renderer_host/media/media_stream_requester.h	(revision 111389)
+++ content/browser/renderer_host/media/media_stream_requester.h	(working copy)
@@ -30,6 +30,17 @@
   // an error.
   virtual void VideoDeviceFailed(const std::string& label, int index) = 0;
 
+  // Called as a reply of a successful call to EnumerateVideoDevices.
+  virtual void VideoDevicesEnumerated(const std::string& label,
+                                      const StreamDeviceInfoArray& devices) = 0;
+  // Called if EnumerateVideoDevices failed.
+  virtual void VideoDevicesEnumerationFailed(const std::string& label) = 0;
+  // Called as a reply of a successful call to OpenVideoDevice.
+  virtual void VideoDeviceOpened(const std::string& label,
+                                 const StreamDeviceInfo& video_device) = 0;
+  // Called if OpenVideoDevice failed.
+  virtual void VideoDeviceOpenFailed(const std::string& label) = 0;
+
  protected:
   virtual ~MediaStreamRequester() {
   }