Roll Dart SDK from 9d279d4 to e2a6772 (1 revision) (#20374)

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': '9d279d41e3677a94bf75f6efb8d5cd98cadd1c7b',
+  'dart_revision': 'e2a67723caf1289a4a496248cc2af2282939e976',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py