Roll src/third_party/skia b3542d9..b4b1005 (6 commits) (#12414)

https://skia.googlesource.com/skia.git/+log/b3542d95da65..b4b1005d485f

git log b3542d9..b4b1005 --date=short --no-merges --format='%ad %ae %s'
2019-09-23 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-09-23 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-09-23 [email protected] Roll third_party/externals/angle2 8be7a4c..a905cbc (5 commits)
2019-09-23 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-09-23 [email protected] Abolish absClear
2019-09-23 [email protected] Use safe computation for adding up YUVASizeInfo total bytes

Created with:
  gclient setdep -r src/third_party/skia@b4b1005d485f

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': 'b3542d95da65043126d84d74ed67af12c17efaa4',
+  'skia_revision': 'b4b1005d485f8518e905d5ba042c0f968f426eff',
 
   # 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: 77f229e55f075830ce3a83b322f842f9
+Signature: 64469c8b4201f617252414c18c3fd44d
 
 UNUSED LICENSES: