support video device enumeration from renderer process.

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
===================================================================
--- content/renderer/render_view_impl.cc	(revision 109718)
+++ content/renderer/render_view_impl.cc	(working copy)
@@ -55,6 +55,7 @@
 #include "content/renderer/load_progress_tracker.h"
 #include "content/renderer/media/audio_message_filter.h"
 #include "content/renderer/media/audio_renderer_impl.h"
+#include "content/renderer/media/media_stream_dispatcher.h"
 #include "content/renderer/media/media_stream_impl.h"
 #include "content/renderer/media/render_media_log.h"
 #include "content/renderer/mhtml_generator.h"
@@ -409,7 +410,9 @@
 
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
   if (command_line.HasSwitch(switches::kEnableMediaStream)) {
+    media_stream_dispatcher_ = new MediaStreamDispatcher(this);
     media_stream_impl_ = new MediaStreamImpl(
+        media_stream_dispatcher(),
         RenderThreadImpl::current()->video_capture_impl_manager());
   }