Fix crash in MouseCursor::CopyOf()

This issue was causing test failures with the latest webrtc roll.

R=mallinath@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/7249005

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@5392 4adac7df-926f-26a2-2b94-8c16560cd09d
1 file changed