Roll Dart SDK from 4ea46a8 to 2a4169b (1 revision) (#21489)

Author: skia-flutter-autoroll

DEPS

@@ -34,7 +34,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/master/DEPS.
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': '4ea46a8b10a1f6fa961588e07ab94fb7f3644e7c',
+  'dart_revision': '2a4169b3cfab3c3bbfab62132dfa3f2b35ba90f5',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py