BUG=220
TEST=convert util and ARGBScale unittests with set LIBYUV_WIDTH=-1280
Review URL: https://webrtc-codereview.appspot.com/1409005

git-svn-id: http://libyuv.googlecode.com/svn/trunk@685 16f28f9a-4ce2-e073-06de-1de4eb20be90