anchor.diff:  }
   
   class FastaCompilerConfiguration extends CompilerConfiguration {
  -  static const String mimeType = "application/x.dill";
  -
  -  final Uri _compilerLocation;
  -
  -  final Uri _plaformDill;
  +  static final _compilerLocation =
  +      Repository.uri.resolve("pkg/front_end/tool/_fasta/compile.dart");
  +
  +  final Uri _platformDill;
   
     final Uri _vmExecutable;
   
  -  final bool _isLegacy;
  -
  -  FastaCompilerConfiguration(Configuration configuration)
  -      : this._(
  -            Repository.uri.resolve("pkg/front_end/tool/_fasta/compile.dart"),
  -            Uri.base
  -                .resolveUri(new Uri.directory(configuration.buildDirectory)),
  -            !configuration.isStrong,
  -            configuration.useSdk,
  -            configuration);
  -
  -  FastaCompilerConfiguration._(this._compilerLocation, Uri buildDirectory,
  -      this._isLegacy, bool useSdk, Configuration configuration)
  -      : _plaformDill = (useSdk
  -                ? buildDirectory.resolve("dart-sdk/lib/_internal/")
  -                : buildDirectory)
  -            .resolve(
  -                _isLegacy ? "vm_platform.dill" : "vm_platform_strong.dill"),
  -        _vmExecutable = useSdk
  -            ? buildDirectory.resolve("dart-sdk/bin/dart")
  -            : buildDirectory.resolve("dart"),
  -        super._subclass(configuration);
  +  bool get _isLegacy => !_configuration.isStrong;
  +
  +  factory FastaCompilerConfiguration(Configuration configuration) {
  +    var buildDirectory =
  +        Uri.base.resolveUri(new Uri.directory(configuration.buildDirectory));
  +
  +    var dillDir = buildDirectory;
  +    if (configuration.useSdk) {
  +      dillDir = buildDirectory.resolve("dart-sdk/lib/_internal/");
  +    }
  +
  +    var suffix = configuration.isStrong ? "_strong" : "";
  +    var platformDill = dillDir.resolve("vm_platform$suffix.dill");
  +
  +    var vmExecutable = buildDirectory
  +        .resolve(configuration.useSdk ? "dart-sdk/bin/dart" : "dart");
  +    return new FastaCompilerConfiguration._(
  +        platformDill, vmExecutable, configuration);
  +  }
  +
  +  FastaCompilerConfiguration._(
  +      this._platformDill, this._vmExecutable, Configuration configuration)
  +      : super._subclass(configuration);
   
     @override
     bool get useDfe => true;
  
positive.code:     if (runtimeConfiguration is! NoneRuntimeConfiguration) {
        throw "--compiler=fasta only supports --runtime=none";
      }
      return <String>[];
    }
  }
  
negative.code:       List<String> sharedOptions,
        List<String> dart2jsOptions,
        List<String> args) {
      var arguments = <String>[];
      for (var argument in args) {
        if (argument != "--ignore-unrecognized-flags") {
          arguments.add(argument);
        }
  