comment-only: add "this may change" warning to SkChecksum.h Review URL: https://codereview.appspot.com/6810054
comment-only: add "this may change" warning to SkChecksum.h
Review URL: https://codereview.appspot.com/6810054

csulmone/skia,csulmone/skia,csulmone/skia,csulmone/skia