Roll src/third_party/skia 7d7aaf46aeb4..858cf233ef71 (1 commits) (flutter#13131)

https://skia.googlesource.com/skia.git/+log/7d7aaf46aeb4..858cf233ef71

git log 7d7aaf46aeb4..858cf233ef71 --date=short --no-merges --format='%ad %ae %s'
2019-10-14 csmartdalton@google.com Call setNeedsStencil() when clearing stencil

Created with:
  gclient setdep -r src/third_party/skia@858cf233ef71

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 csmartdalton@google.com 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
TBR=csmartdalton@google.com

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': '7d7aaf46aeb450b983ff5ac8833d6ca3065671a8',
+  'skia_revision': '858cf233ef71ec1b4fee9dc0992f8889a96e6ceb',
 
   # 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: 678a19286a2d915457fa21f6baaf2976
+Signature: 4556ee934313e3bb4925207d778ec2c4
 
 UNUSED LICENSES: