anchor.diff:      negatable: false,
       abbr: 'h',
       help: 'Prints help output.',
  +  )
  +  ..addOption(
  +    argHost,
  +    defaultsTo: 'localhost',
  +    help: 'Hostname to serve DevTools on.',
     )
     ..addOption(
       argPort,
  
positive.code:     serviceProtocolUri: vmUri,
      profileFilename: profileAbsoluteFilename,
      verboseMode: verboseMode,
    );
  }
  
  
negative.code:   final numPortsToTry =
        args[argTryPorts] != null ? int.tryParse(args[argTryPorts]) ?? 1 : 1;
    final bool verboseMode = args[argVerbose];
    final String hostname = args[argHost];
  
    // Support collecting profile data.
    final String vmUri = args[argVmUri];
  