Roll src/third_party/skia 71c0e9422038..c9eeab3d85b9 (4 commits) (#8418)

https://skia.googlesource.com/skia.git/%2Blog/71c0e9422038..c9eeab3d85b9

git log 71c0e94220380f4cbb3a8ba462ef9036fa7ab1ff..c9eeab3d85b9c85e49a4d8228ba7468072e2bb0d --date=short --no-merges --format=%ad %ae %s
2019-04-02 bungeman@google.com Remove Skia version number.
2019-04-02 mtklein@google.com update some FM flags
2019-04-02 michaelludwig@google.com Do not lose existing paint shaders when drawing alpha images
2019-04-02 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 (jlavrova@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': '71c0e94220380f4cbb3a8ba462ef9036fa7ab1ff',
+  'skia_revision': 'c9eeab3d85b9c85e49a4d8228ba7468072e2bb0d',
 
   # 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: 2d6c6916c1b3db8760ed776b42eb606f
+Signature: 27640e6e3ae5e29abe45ac591b5f2a30
 
 UNUSED LICENSES: