Roll Dart SDK from 99553e1 to b0a1531 (1 revision) (#34549)

Author: skia-flutter-autoroll

DEPS

@@ -45,7 +45,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/main/DEPS.
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': '99553e192d272bee378fe920bec21748b9c3c454',
+  'dart_revision': 'b0a15318b2e86ae0d4d14c40d1014a1b500a8e19',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py