Roll Skia from 7990401d716a to b4b9c76206f3 (1 revision) (flutter/engine#43681)

https://skia.googlesource.com/skia.git/+log/7990401d716a..b4b9c76206f3

2023-07-14 johnstiles@google.com Reland "Fix swizzled compound assignment with lvalue side-effects in Metal."

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 brianosman@google.com,kjlubick@google.com,rmistry@google.com,zra@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': '7990401d716ad7217f2cfc4f3bb0afba0df33a7e',
+  'skia_revision': 'b4b9c76206f34ad613f587250895c9f5fc1bd32a',
 
   # 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: af939d0fdca22e8a636d6adc43245eb9
+Signature: 44157e800c284870a4fbc98737cc0102
 
 ====================================================================================================
 LIBRARY: etc1