Currently disposing Java peer connection object will result in auto release of media streams and media tracks added to peer connection. Add an option to allow application to own video track so it can be kept after peer connection is destroyed. R=jiayl@webrtc.org, wzh@webrtc.org Review URL: https://codereview.webrtc.org/1333363002 . Cr-Commit-Position: refs/heads/master@{#9946}