Roll Skia from 37940afc0caf to a6de6d2366e4 (1 revision) (flutter/engine#29870)

https://skia.googlesource.com/skia.git/+log/37940afc0caf..a6de6d2366e4

2021-11-21 skia-autoroll@skia-public.iam.gserviceaccount.com Roll SK Tool from 055155207d7e to 0024349d8141

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 jsimmons@google.com,jlavrova@google.com on the revert to ensure that a human
is aware of the problem.

To file a bug in Skia: https://bugs.chromium.org/p/skia/issues/entry
To file a bug in Flutter: https://github.com/flutter/flutter/issues/new/choose

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/main/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': '37940afc0caf5a68c3c17e28d23f3c101b73d6fd',
+  'skia_revision': 'a6de6d2366e415bce5c2fe28049cb7525d1c8db8',
 
   # WARNING: DO NOT EDIT canvaskit_cipd_instance MANUALLY
   # See `lib/web_ui/README.md` for how to roll CanvasKit to a new version.

engine/src/flutter/ci/licenses_golden/licenses_skia

@@ -1,4 +1,4 @@
-Signature: 46e28e07932d1111041e3ae737d16c06
+Signature: bfcbe875923f1180b58e10fbbd074952
 
 UNUSED LICENSES: