Roll Dart SDK from 8f1a96317589 to 8572b5c0f6dc (1 revision) (flutter#21686)

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': '8f1a96317589c23685b2f7a097953cea0396ac23',
+  'dart_revision': '8572b5c0f6dc864cda98f5b4d23ed07e4c89a231',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py