Roll Skia from d4acfbe0b001 to c91cad775529 (1 revision) (flutter/engine#53924)

https://skia.googlesource.com/skia.git/+log/d4acfbe0b001..c91cad775529

2024-07-16 michaelludwig@google.com [graphite] Automate begin/endStruct() calls in KeyHelpers

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,nicolettep@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://issues.skia.org/issues/new?component=1389291&template=1850622

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

DEPS

@@ -14,7 +14,7 @@ vars = {
   'flutter_git': 'https://flutter.googlesource.com',
   'skia_git': 'https://skia.googlesource.com',
   'llvm_git': 'https://llvm.googlesource.com',
-  'skia_revision': 'd4acfbe0b001c7df1a5165b43bd8efbd43743ed4',
+  'skia_revision': 'c91cad77552979f94305b36cc62fd152af442538',
 
   # 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: f2c58d27aa6769c7caa03d5ae57a22fc
+Signature: aa2979eba04022008f47cd22326de004
 
 ====================================================================================================
 LIBRARY: etc1