BUG=196
TESTED=libyuv_unittest --gtest_filter=*ABGRToARGB*
Review URL: https://webrtc-codereview.appspot.com/1166006

git-svn-id: http://libyuv.googlecode.com/svn/trunk@595 16f28f9a-4ce2-e073-06de-1de4eb20be90