anchor.diff:          values: System.names,
           defaultsTo: Platform.operatingSystem,
           hide: true),
  +    _Option('sanitizer', 'Sanitizer in which to run the tests.',
  +        defaultsTo: Sanitizer.none.name, values: ['all', ...Sanitizer.names]),
       _Option(
           'named_configuration',
           '''The named test configuration that supplies the values for all
  
positive.code:     }
  
      var runtimeNames = data["runtime"] as String;
      var runtimes = <Runtime>[];
      if (runtimeNames != null) {
        runtimes.addAll(runtimeNames.split(",").map(Runtime.find));
      }
  
      var compilerNames = data["compiler"] as String;
      var compilers = <Compiler>[];
      if (compilerNames != null) {
        compilers.addAll(compilerNames.split(",").map(Compiler.find));
      }
  
      // Pick default compilers or runtimes if only one or the other is provided.
      if (runtimes.isEmpty) {
  
negative.code: arm, armv6, arm64,
  simarm, simarmv6, simarm64, arm_x64''',
          abbr: 'a',
          values: ['all', ...Architecture.names],
          defaultsTo: Architecture.x64.name,
          hide: true),
      _Option('system', 'The operating system to run tests on.',
  