Roll Dart SDK from c153c5259e62 to 4f9623f024ab (2 revisions) (flutter#174250)

https://dart.googlesource.com/sdk.git/+log/c153c5259e62..4f9623f024ab

2025-08-22 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com
Version 3.10.0-127.0.dev
2025-08-21 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com
Version 3.10.0-126.0.dev

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/dart-sdk-flutter
Please CC dart-vm-team@google.com,jimgraham@google.com on the revert to
ensure that a human
is aware of the problem.

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https://github.com/flutter/flutter/issues/new/choose

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Author: engine-flutter-autoroll

DEPS

@@ -56,7 +56,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/main/DEPS
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': 'c153c5259e62a0cfdb2dea2ed001bfa7b384d0a5',
+  'dart_revision': '4f9623f024ab4c07ccb4250fcf4d8fbc8dd497fc',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py