BUG=none
TEST=./libyuv_unittest --gtest_filter=*ARGBScale*
Review URL: https://webrtc-codereview.appspot.com/964016

git-svn-id: http://libyuv.googlecode.com/svn/trunk@494 16f28f9a-4ce2-e073-06de-1de4eb20be90