Roll Dart SDK from 0716e2d63f15 to bbe6bb982349 (2 revisions) (flutter#19868)

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': '0716e2d63f15cf86ef035be5f2c729481e918cfe',
+  'dart_revision': 'bbe6bb9823495574917c75634b1f8a2a8099086c',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py