Roll Dart SDK from e9693f1 to 4c8147b (1 revision) (#24397)

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': 'e9693f1b24011ec40a32a9b1c415c148525bfa24',
+  'dart_revision': '4c8147b7b41e19164ce35fc75ac0589f3f48f27e',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py