Roll Skia from afd8a6c to b6d158a (3 revisions)

https://skia.googlesource.com/skia.git/+log/afd8a6c6ae87..b6d158aaf3dd

2020-05-23 reed@google.com use SkOnce for singleton patheffect
2020-05-23 skia-recreate-skps@skia-swarming-bots.iam.gserviceaccount.com Update Go Deps
2020-05-22 herb@google.com turn off 2M glyph test

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/skia-flutter-autoroll
Please CC lovisolo@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

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

Author: skia-flutter-autoroll

DEPS

@@ -26,7 +26,7 @@ vars = {
   'skia_git': 'https://skia.googlesource.com',
   # OCMock is for testing only so there is no google clone
   'ocmock_git': 'https://github.com/erikdoe/ocmock.git',
-  'skia_revision': 'afd8a6c6ae87d9462b0094e8c0009b226cc45f1f',
+  'skia_revision': 'b6d158aaf3ddd44a2b6bb2428de65b94645427d6',
 
   # When updating the Dart revision, ensure that all entries that are
   # dependencies of Dart are also updated to match the entries in the

ci/licenses_golden/licenses_skia

@@ -1,4 +1,4 @@
-Signature: 34c18e2491e24617448b31acb23a9840
+Signature: 146315b65820981efa22a0f118591750
 
 UNUSED LICENSES: