Roll src/third_party/skia be91f062d70e..a7ad120fb6c1 (3 commits) (#9968)

https://skia.googlesource.com/skia.git
/compare/be91f062d70e..a7ad120fb6c1

git log be91f062d70e2f317298632f172bde85255af564..a7ad120fb6c12a614047e5904f78e04e1f39b1d9 --date=short --no-merges --format=%ad %ae %s
2019-07-19 csmartdalton@google.com Fix an error check re: sample variables
2019-07-20 skia-recreate-skps@skia-swarming-bots.iam.gserviceaccount.com Update Go deps
2019-07-19 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).

The AutoRoll server is located here: https://autoroll.skia.org/r/skia-flutter-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 (nifong@google.com), and stop
the roller if necessary.

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': 'be91f062d70e2f317298632f172bde85255af564',
+  'skia_revision': 'a7ad120fb6c12a614047e5904f78e04e1f39b1d9',
 
   # 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

-Signature: 17367123156ab295a080592a30b2459b
+Signature: ac28c04bc64b6d7c8f5ecb934b2efa8b
 
 UNUSED LICENSES: