Roll Dart SDK from 50eca21d80c4 to dffc5f3f9be6 (1 revision) (flutter#178603)

https://dart.googlesource.com/sdk.git/+log/50eca21d80c4..dffc5f3f9be6

2025-11-15 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com
Version 3.11.0-141.0.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 aaclarke@google.com,dart-vm-team@google.com on the revert to
ensure that a human
is aware of the problem.

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

Author: engine-flutter-autoroll

DEPS

@@ -57,7 +57,7 @@ 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': '50eca21d80c4b7b275ef52203689b271db106390',
+  'dart_revision': 'dffc5f3f9be65fc4d86031f079078c6db01a2f76',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py