stop using (deprecated) setClipRegion, add flag for new clipop type

future skia CL that will migrate to specialized type for clipops : https://codereview.chromium.org/2355483002

BUG=skia:3191, skia:5773

Review-Url: https://codereview.chromium.org/2355583002
Cr-Commit-Position: refs/heads/master@{#419574}
3 files changed