Roll Dart SDK from 1aa700abeec1 to 518bf3997ba6 (2 revisions) (#181118)

https://dart.googlesource.com/sdk.git/+log/1aa700abeec1..518bf3997ba6

2026-01-18 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com
Version 3.12.0-43.0.dev
2026-01-18 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com
Version 3.12.0-42.0.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.

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

diff --git a/DEPS b/DEPS
index d6ab0a0..1e4aa5e 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': '1aa700abeec1408910bd19fc3fc807e290778cff',
+  'dart_revision': '518bf3997ba6c7d7ee19d19b7a46bcb6942159f7',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py