anchor.diff:    if (platform.isWindows) {
       /// The possible locations where the chrome executable can be located on windows.
       final List<String> kWindowsPrefixes = <String>[
  -      platform.environment['LOCALAPPDATA'],
  -      platform.environment['PROGRAMFILES'],
  -      platform.environment['PROGRAMFILES(X86)'],
  +      if (platform.environment.containsKey('LOCALAPPDATA'))
  +        platform.environment['LOCALAPPDATA']!,
  +      if (platform.environment.containsKey('PROGRAMFILES'))
  +        platform.environment['PROGRAMFILES']!,
  +      if (platform.environment.containsKey('PROGRAMFILES(X86)'))
  +        platform.environment['PROGRAMFILES(X86)']!,
       ];
       final String windowsPrefix = kWindowsPrefixes.firstWhere((String prefix) {
         if (prefix == null) {
  
positive.code:   /// [skipCheck] does not attempt to make a devtools connection before returning.
    Future<Chromium> launch(String url, {
      bool headless = false,
      int debugPort,
      bool skipCheck = false,
      Directory cacheDir,
    }) async {
      if (currentCompleter.isCompleted) {
        throwToolExit('Only one instance of chrome can be started.');
  
negative.code:       // launching more processes.
        unawaited(process.exitCode.timeout(const Duration(seconds: 1), onTimeout: () {
          process.kill();
          // sigterm
          return 15;
        }));
      }
    }
  