Roll src/third_party/skia ad21d47cfa8d..d860a78fd60c (2 commits) (flutter#13794)

https://skia.googlesource.com/skia.git/+log/ad21d47cfa8d..d860a78fd60c

git log ad21d47cfa8d..d860a78fd60c --date=short --no-merges --format='%ad %ae %s'
2019-11-12 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/angle2 012d15196023..e33c1582b4bc (6 commits)
2019-11-12 herb@google.com WS: SkStrike

Created with:
  gclient setdep -r src/third_party/skia@d860a78fd60c

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 halcanary@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/+/master/autoroll/README.md

Bug: None
TBR=halcanary@google.com

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': 'ad21d47cfa8d9adb2145216c5e514d978d649096',
+  'skia_revision': 'd860a78fd60c6c06d5de16863b6ccd8b008565ac',
 
   # 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: e2fba7540b7c9a199110c06d578872b8
+Signature: 9b4cfb54c01eb26dfc1c57974b36fe04
 
 UNUSED LICENSES: