Roll Skia from 4dfa977 to 6c5e78d (6 revisions)

https://skia.googlesource.com/skia.git/+log/4dfa9774300c..6c5e78d09940

2020-11-24 49699333+dependabot[bot]@users.noreply.github.com Bump bl from 4.0.2 to 4.0.3 in /tools/perf-canvaskit-puppeteer
2020-11-24 [email protected] Add supporting function for finding image use in layers
2020-11-24 [email protected] Move conservative bounds tracking from SkCanvas to SkNoPixelsDevice
2020-11-24 [email protected] Add cusp detection to GrPathUtils::findCubicConvex180Chops
2020-11-24 [email protected] Remove unused parameter in vk bindDescriptorSets.
2020-11-24 [email protected] implement a whole slew of arm64 ops

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/+doc/master/autoroll/README.md

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': '4dfa9774300cd94989fbbe21d21a2e2e25f8878e',
+  'skia_revision': '6c5e78d0994081f59a9d0c6b6913bbb35b8b1ec2',
 
   # 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: 144c5676ababdae963fdafa8b91a9726
+Signature: 62771efb7b2499a309ec896459eec7d2
 
 UNUSED LICENSES: