initial clean up of pdf clipping

clipstack is always available, canvas checks for empty clips up-front

Next step is to clarify if PDF wants to use Regions or Clipstack for its clipping (but not both)

Change-Id: Iaf1fa35160291e08c33ff61114557deff72304b3
Reviewed-on: https://skia-review.googlesource.com/8692
Reviewed-by: Hal Canary <halcanary@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed