Revert 7302 "Roll chromium revision: 6455c69:2687a76"

> Roll chromium revision: 6455c69:2687a76
> 
> Pick up the libvpx roll: https://codereview.chromium.org/597703004/
> 
> R=johannkoenig@google.com
> TBR=ajm@google.com
> 
> Review URL: https://webrtc-codereview.appspot.com/23789004

TBR=marpan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/22789004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7304 4adac7df-926f-26a2-2b94-8c16560cd09d