Roll Dart SDK from 8afe9875a6d7 to 28a3cd203923 (2 revisions) (#19476)

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': '8afe9875a6d7acc2a002e2aad58de0934537387a',
+  'dart_revision': '28a3cd203923f95ffd3cd850c59f35732d18e67d',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py

ci/licenses_golden/licenses_third_party

-Signature: c4d6b5af377ae6cdedefdd37573b41ef
+Signature: e24e2f80b10045206251a346340309ef
 
 UNUSED LICENSES: