Roll Skia from f661ec788b14 to 798021ada347 (3 revisions) (#23960)

https://skia.googlesource.com/skia.git/+log/f661ec788b14..798021ada347

2021-01-26 johnstiles@google.com Add unit test for control statements in do-while loop.
2021-01-26 johnstiles@google.com Revert "Reland "Enable _LIBCPP_DEBUG in Clang for non-Xcode-based debug builds.""
2021-01-26 adlai@google.com Redux merging adjacent ops tasks

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 nifong@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/+doc/master/autoroll/README.md

DEPS

@@ -27,7 +27,7 @@ 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': 'f661ec788b147da97ca73ed349096a194902af56',
+  'skia_revision': '798021ada347ef676d7408e9fd34744dfa0f387d',
 
   # 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: 6db5d7f20f0f0dfc58437fa27b140c3f
+Signature: ff4444a2533de2d21ab06e2ffe1cc2c0
 
 UNUSED LICENSES: