Roll external/skia 0221e8b22..8fae51b69 (3 commits)

https://skia.googlesource.com/skia.git/+log/0221e8b22..8fae51b69

2019-05-13 herb@google.com Introduce SkStrikeSpecStorage.
2019-05-13 robertphillips@google.com Standardize DDL images to RGBA
2019-05-13 michaelludwig@google.com Use per-edge AA flags to respect mixed AA between clip and draw

The AutoRoll server is located here: https://autoroll-internal.skia.org/r/android-master-autoroll

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.

Test: Presubmit checks will test this change.
Change-Id: Ib1ff3fe031145b52ccd4858b19e7734ce334ecd3
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.