remove PLAIN_ENUM flag for SkClipOp

BUG=skia:

Change-Id: Ie87c3e11df74fecf32217e2039ce46bea9ff4ab7
Reviewed-on: https://skia-review.googlesource.com/6033
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed