BUG=208
TEST=out\release\libyuv_unittest --gtest_filter=*ARGBScale*640*

Review URL: https://webrtc-codereview.appspot.com/1303006

git-svn-id: http://libyuv.googlecode.com/svn/trunk@664 16f28f9a-4ce2-e073-06de-1de4eb20be90