Roll Dart SDK from 18f6751c5ccc to 6b2c3716be54 (1 revision) (#180252)

https://dart.googlesource.com/sdk.git/+log/18f6751c5ccc..6b2c3716be54

2025-12-23 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com
Version 3.11.0-272.0.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 codefu@google.com,dart-vm-team@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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https://issues.skia.org/issues/new?component=1389291&template=1850622

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DEPS

diff --git a/DEPS b/DEPS
index 4934c8e..23bf3da 100644
--- a/DEPS
+++ b/DEPS
@@ -59,7 +59,7 @@
   # updated revision list of existing dependencies. You will need to
   # gclient sync before and after update deps to ensure all deps are updated.
   # updated revision list of existing dependencies.
-  'dart_revision': '18f6751c5cccfe417264b4c657d253cb75829334',
+  'dart_revision': '6b2c3716be5454108fbabfb7f6f4a6adc7012835',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py