add unittests for clip-state queries

BUG=skia:

Change-Id: I6f8d5a0e78c5b41caa6c6388f7f2ace050ed08ac
Reviewed-on: https://skia-review.googlesource.com/9171
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed