Use the libvpx rev from Chromium's DEPS, not the Chromium rev.

R=kjellander@webrtc.org, marpan@google.com

Review URL: https://webrtc-codereview.appspot.com/18639004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6559 4adac7df-926f-26a2-2b94-8c16560cd09d