Roll Dart SDK from aa0fea71185b to 3870a33d25fb (1 revision) (flutter#24649)

Author: skia-flutter-autoroll

DEPS

@@ -35,7 +35,7 @@ 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': 'aa0fea71185b6c3a763ff3875ea0973a6729a04d',
+  'dart_revision': '3870a33d25fb02ffada98fd22d385f4405dd69d1',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py