Roll src/third_party/skia 858cf233ef71..55f9cba6e2e7 (3 commits) (flutter#13133)

https://skia.googlesource.com/skia.git/+log/858cf233ef71..55f9cba6e2e7

git log 858cf233ef71..55f9cba6e2e7 --date=short --no-merges --format='%ad %ae %s'
2019-10-15 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/angle2 fede5cb664d9..2d0e5b554d4f (4 commits)
2019-10-15 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/swiftshader 1c462ebc904c..a27dfcf868bf (3 commits)
2019-10-15 skia-autoroll@skia-public.iam.gserviceaccount.com Roll ../src e034419fbc6a..083c52f74ac2 (362 commits)

Created with:
  gclient setdep -r src/third_party/skia@55f9cba6e2e7

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': '858cf233ef71ec1b4fee9dc0992f8889a96e6ceb',
+  'skia_revision': '55f9cba6e2e7b8ff3ba4f1453349db26e547cb28',
 
   # 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: 4556ee934313e3bb4925207d778ec2c4
+Signature: ab7888ae8d5b7010367d20243973f9de
 
 UNUSED LICENSES: