BUG=181
TESTED=c:\intelsde\sde -hsw -- out\release\libyuv_unittest.exe --gtest_filter=*ARGBToI420*
Review URL: https://webrtc-codereview.appspot.com/1091010

git-svn-id: http://libyuv.googlecode.com/svn/trunk@567 16f28f9a-4ce2-e073-06de-1de4eb20be90