Important as OnLoadUpdate() won't be called on the worker thread and the list of streams can't be concurrently modified while delivering this callback to all send streams. R=stefan@webrtc.org BUG=1788 Review URL: https://webrtc-codereview.appspot.com/22959004 git-svn-id: http://webrtc.googlecode.com/svn/trunk@7395 4adac7df-926f-26a2-2b94-8c16560cd09d