anchor.diff:  // that would replace api used below. This api was made private in
   // an effort to discourage further use.
   // ignore_for_file: implementation_imports
  +import 'package:front_end/src/api_prototype/compiler_options.dart'
  +    show CompilerOptions, parseExperimentalFlags;
   import 'package:front_end/src/api_unstable/vm.dart';
   import 'package:kernel/ast.dart';
   import 'package:kernel/binary/ast_to_binary.dart';
  
positive.code:           'used, and where dill filesize does not matter, and the gain is '
            'improved speed.',
        defaultsTo: false,
        hide: true);
  
  String usage = '''
  
negative.code:       ..sdkSummary = sdkRoot.resolve(platformKernelDill)
        ..verbose = options['verbose']
        ..embedSourceText = options['embed-source-text']
        ..experimentalFlags = parseExperimentalFlags(
            options['enable-experiment'], (msg) => errors.add(msg))
        ..onDiagnostic = (DiagnosticMessage message) {
          bool printMessage;
          switch (message.severity) {
  