Roll src/third_party/skia e68b5bd4e6e9..bff2939b6249 (1 commits) (flutter/engine#10248)

https://skia.googlesource.com/skia.git
/compare/e68b5bd4e6e9..bff2939b6249

git log e68b5bd4e6e9bdf5a69932fafbd17817572971e4..bff2939b624903efa4e99c9095c778f3edf63e6e --date=short --no-merges --format=%ad %ae %s
2019-07-30 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/swiftshader 3575550a711b..e6092f3bc901 (9 commits)

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 (benjaminwagner@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': 'e68b5bd4e6e9bdf5a69932fafbd17817572971e4',
+  'skia_revision': 'bff2939b624903efa4e99c9095c778f3edf63e6e',
 
   # When updating the Dart revision, ensure that all entries that are
   # dependencies of Dart are also updated to match the entries in the

engine/src/flutter/ci/licenses_golden/licenses_skia

@@ -1,4 +1,4 @@
-Signature: e2f7623c1df9ffe1452e83e757a5df47
+Signature: 5cae9182665bb197af3f965201000966
 
 UNUSED LICENSES: