Roll src/third_party/skia e99e8dae066a..31ba6feaf6b3 (3 commits) (#7477)

https://skia.googlesource.com/skia.git/%2Blog/e99e8dae066a..31ba6feaf6b3

git log e99e8dae066a1db6c52669ea26a3f6076953fba4..31ba6feaf6b34019c0869edf3ae3b02c19731022 --date=short --no-merges --format=%ad %ae %s
2019-01-14 reed@google.com unflatten directly to font for legacy skps
2019-01-14 herb@google.com Add buffers for Mask drawing in preparation for bulk API
2019-01-07 halcanary@google.com Documentation: SkCanvas

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 (halcanary@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': 'e99e8dae066a1db6c52669ea26a3f6076953fba4',
+  'skia_revision': '31ba6feaf6b34019c0869edf3ae3b02c19731022',
 
   # 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: 2fbbe4b1e82581f9c0eadc182fb3df4b
+Signature: 7f8f553b5b5fbf13c71e6c1a711418db
 
 UNUSED LICENSES: