Roll src/third_party/skia 18531cde2ab7..9a8b846baf43 (1 commits) (flutter#12360)

https://skia.googlesource.com/skia.git/+log/18531cde2ab7..9a8b846baf43

git log 18531cde2ab7..9a8b846baf43 --date=short --no-merges --format='%ad %ae %s'
2019-09-19 [email protected] Particles: Sub-effect spawning and some slight refactoring

Created with:
  gclient setdep -r src/third_party/skia@9a8b846baf43

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/skia-flutter-autoroll
Please CC [email protected] on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

Bug: None
[email protected]

Author: skia-flutter-autoroll

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': '18531cde2ab757d82d3934fbac6c698e7b53cb3b',
+  'skia_revision': '9a8b846baf43752fa8cddbfa04b19b7707580d43',
 
   # 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

@@ -1,4 +1,4 @@
-Signature: 31cdf3333929b8a9d78e94861aed27f0
+Signature: f9408fc447605fa361acfd80fcff1feb
 
 UNUSED LICENSES: