Roll Skia from 981146e6305d to 6f2b2e94ebbd (3 revisions) (flutter/engine#43871)

https://skia.googlesource.com/skia.git/+log/981146e6305d..6f2b2e94ebbd

2023-07-20 aeubanks@google.com Fix newly warned -Wconstant-logical-operand
2023-07-20 johnstiles@google.com Add WGSL support for uniforms inside interface blocks.
2023-07-20 skia-autoroll@skia-public.iam.gserviceaccount.com Roll vulkan-deps from e1c3b16d5aa5 to 13599b120a68 (8 revisions)

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 bdero@google.com,brianosman@google.com,rmistry@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

@@ -18,7 +18,7 @@ vars = {
   'llvm_git': 'https://llvm.googlesource.com',
   # OCMock is for testing only so there is no google clone
   'ocmock_git': 'https://github.com/erikdoe/ocmock.git',
-  'skia_revision': '981146e6305dc5ff7726d5fa0f0df9a7b311cb32',
+  'skia_revision': '6f2b2e94ebbd4a2a5c031ac06bcd3f2d203034a7',
 
   # 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: f515ba2926afce76bd817381c9c7252e
+Signature: 0d07bb62e3dd3d4a1fc8fd0f3b886ed4
 
 ====================================================================================================
 LIBRARY: etc1