BUG=253
TESTED=libyuvTest.TestCopyPlane
R=wuwang@google.com

Review URL: https://webrtc-codereview.appspot.com/2060006

git-svn-id: http://libyuv.googlecode.com/svn/trunk@765 16f28f9a-4ce2-e073-06de-1de4eb20be90