Un-breaks peerconnection_client which would instantly use-after-free on an allocated VCM because it wasn't building a scoped_refptr so all references to the VCM were dropped. BUG=webrtc:5229 TBR=tommi@webrtc.org TEST=Run peerconnection_client locally, verify that there's no crash. Review URL: https://codereview.webrtc.org/1817953005 . Cr-Commit-Position: refs/heads/master@{#12088}