Roll Skia from 643fae1b1559 to f9794b94c518 (1 revision) (flutter/engine#42389)

https://skia.googlesource.com/skia.git/+log/643fae1b1559..f9794b94c518

2023-05-28 skia-autoroll@skia-public.iam.gserviceaccount.com Roll vulkan-deps from 850909c8c350 to 6e41699c8a41 (1 revision)

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,robertphillips@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': '643fae1b1559b3dd5e200b180b3df7f4f33c8c00',
+  'skia_revision': 'f9794b94c518795ce79c818c1f9b1a1f92ed9307',
 
   # WARNING: DO NOT EDIT canvaskit_cipd_instance MANUALLY
   # See `lib/web_ui/README.md` for how to roll CanvasKit to a new version.