BUG=253
TEST=out\release\libyuv_unittest --gtest_filter=*Add*
R=dingkai@google.com, nfullagar@chromium.org

Review URL: https://webrtc-codereview.appspot.com/1972004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@746 16f28f9a-4ce2-e073-06de-1de4eb20be90