anchor.diff:                                  _stderr._stream._nativeSocket,
                                   _exitHandler._nativeSocket,
                                   status);
  +    _environment = null;  // The environment will not be needed going forward.
       if (!success) {
         throw new ProcessException(_path,
                                    _arguments,
  
positive.code:                                   _stderr._stream._nativeSocket,
                                    _exitHandler._nativeSocket,
                                    status);
        if (!success) {
          completer.completeError(
              new ProcessException(_path,
  
negative.code:     }
  
      _environment = [];
      var environmentEntryHandler = (key, value) {
        if (key is !String || value is !String) {
          throw new ArgumentError(
          "Environment key or value is not a string: ($key, $value)");
        }
        _environment.add('$key=$value');
      };
      if (environment != null) {
        if (environment is !Map) {
          throw new ArgumentError("Environment is not a map: $environment");
        }
        environment.forEach(environmentEntryHandler);
      }
      if (includeParentEnvironment) {
        Platform.environment.forEach(environmentEntryHandler);
      }
  
      // stdin going to process.
      _stdin = new _StdSink(new _Socket._writePipe());
  