Add GMs and benchs for concave Analytic AA

BUG=skia:

Change-Id: I2ed6e2c4f81dc9d5c53b07332c0063f42c6b3c79
Reviewed-on: https://skia-review.googlesource.com/5771
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Yuqian Li <liyuqian@google.com>
2 files changed