Roll src/third_party/skia 1c0b05afdef8..a76fad2d494a (4 commits) (#8665)

https://skia.googlesource.com/skia.git/%2Blog/1c0b05afdef8..a76fad2d494a

git log 1c0b05afdef8c0366926d3a5cdbe828ff122cfe2..a76fad2d494af8bde8c3fb34a2de2b359beebab1 --date=short --no-merges --format=%ad %ae %s
2019-04-21 skia-recreate-skps@skia-swarming-bots.iam.gserviceaccount.com Update go_deps asset
2019-04-20 skia-recreate-skps@skia-swarming-bots.iam.gserviceaccount.com Update go_deps asset
2019-04-18 jvanverth@google.com Add Metal support for dynamic buffers.
2019-04-19 reed@google.com Add secret draw-behind method

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 (mtklein@google.com), and stop
the roller if necessary.

DEPS

@@ -23,7 +23,7 @@ vars = {
   'fuchsia_git': 'https://fuchsia.googlesource.com',
   'github_git': 'https://github.com',
   'skia_git': 'https://skia.googlesource.com',
-  'skia_revision': '1c0b05afdef8c0366926d3a5cdbe828ff122cfe2',
+  'skia_revision': 'a76fad2d494af8bde8c3fb34a2de2b359beebab1',
 
   # 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: 60d8d8f89167f18c7f8302cc7bbe217f
+Signature: e7ac0cfd2e59c61abc7a7430cdf35401
 
 UNUSED LICENSES: