Roll Dart SDK from 12e49f395fd9 to 3e139f5d0720 (1 revision) (#52256)

https://dart.googlesource.com/sdk.git/+log/12e49f395fd9..3e139f5d0720

2024-04-19 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com Version 3.5.0-78.0.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-engine
Please CC dart-vm-team@google.com,jsimmons@google.com on the revert to ensure that a human
is aware of the problem.

To file a bug in Flutter Engine: 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: skia-flutter-autoroll

DEPS

@@ -62,7 +62,7 @@ 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': '12e49f395fd9185beebb3e9ff62b72910584d91d',
+  'dart_revision': '3e139f5d0720b5a7e991dade06609992958759f5',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py