Hide exotic clipops, with a private rename for internal use

BUG=skia:

Change-Id: I6c320a8c7fa501771d93c191c4657452cc9f2e03
Reviewed-on: https://skia-review.googlesource.com/5844
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
5 files changed