This is very similar to the changes in
https://code.google.com/p/webrtc/source/detail?r=6938

TESTED=gclient sync and runhooks on Mac and Linux + building successfully.
R=fbarchard@chromium.org

Review URL: https://webrtc-codereview.appspot.com/24619004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@1089 16f28f9a-4ce2-e073-06de-1de4eb20be90