Roll Dart SDK from 12fded61a2bc to a06d469024fd (1 revision) (flutter#22623)

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': '12fded61a2bc265f633d1e030c8d33befe40c825',
+  'dart_revision': 'a06d469024fd8d94691e32a0525308aabfa50f51',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py