Roll external/skia 719a69ca5..2f3637bf2 (2 commits)

https://skia.googlesource.com/skia.git/+log/719a69ca5..2f3637bf2

2019-05-06 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/angle2 ddc4d33a259a..6f0c5b8dd5f2 (15 commits)
2019-05-06 skia-autoroll@skia-public.iam.gserviceaccount.com Roll ../src b81b70981d9b..e300e8fa69a2 (429 commits)

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: Idd3578f5f6eb5c9eebc8d250f69ba14c15dd0e52
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.