enable video capture to support sharing across multiple renderer processes

media/video/capture/win/video_capture_device_win.cc

Index: media/video/capture/win/video_capture_device_win.cc
===================================================================
--- media/video/capture/win/video_capture_device_win.cc	(revision 106642)
+++ media/video/capture/win/video_capture_device_win.cc	(working copy)
@@ -333,6 +333,8 @@
     return;
 
   observer_ = observer;
+  observer_->OnDeviceState(true);
+
   // Get the camera capability that best match the requested resolution.
   const int capability_index = GetBestMatchedCapability(width, height,
                                                         frame_rate);
@@ -466,6 +468,7 @@
     return;
   }
 
+  observer_->OnDeviceState(false);
   state_ = kIdle;
 }