Roll Dart SDK from c938793e2d6f to fe83360d3a7c (1 revision) (flutter#21440)

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': 'c938793e2d6f317093292ffffea648d79d204120',
+  'dart_revision': 'fe83360d3a7c80ee34d4d5ef67ca6b52d8ba35b0',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py