Implement 'toffset' extension in VideoSendStream.

BUG=2229
R=holmer@google.com, stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2199004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@4722 4adac7df-926f-26a2-2b94-8c16560cd09d
4 files changed