BUG=none
TEST=libyuvTest.ARGBToI422_CvsOPT (836 ms)
Review URL: https://webrtc-codereview.appspot.com/637006

git-svn-id: http://libyuv.googlecode.com/svn/trunk@278 16f28f9a-4ce2-e073-06de-1de4eb20be90