Since VCI::IF() fires a callback it risks a call back into VCI on the same
stack. Failing to acquire _apiCs before _callbackCs means this is a lock
inversion and deadlock results. By acquiring _apiCs first no lock inversion
occurs and the deadlock is removed.
BUG=3434
R=mflodman@webrtc.org
Review URL: https://webrtc-codereview.appspot.com/14629004
git-svn-id: http://webrtc.googlecode.com/svn/trunk@6353 4adac7df-926f-26a2-2b94-8c16560cd09d