anchor.diff:  
   import 'package:pedantic/pedantic.dart';
   
  +import 'package:path/path.dart' as path;
   import 'package:test_core/src/util/io.dart'; // ignore: implementation_imports
   
   import 'browser.dart';
  +import 'common.dart';
  +import 'environment.dart';
   import 'firefox_installer.dart';
  -import 'common.dart';
   
   /// A class for running an instance of Firefox.
   ///
  
positive.code:       ];
  
        final Process process =
            await Process.start(installation.executable, args,
              workingDirectory: dir);
  
        remoteDebuggerCompleter.complete(
            getRemoteDebuggerUrl(Uri.parse('http://localhost:$kDevtoolsPort')));
  
        unawaited(process.exitCode
            .then((_) => Directory(dir).deleteSync(recursive: true)));
  
        return process;
      }, remoteDebuggerCompleter.future);
  
negative.code:         infoLog: isCirrus ? stdout : DevNull(),
        );
  
        // Using a profile on opening will prevent popups related to profiles.
        final _profile = '''
  user_pref("browser.shell.checkDefaultBrowser", false);
  user_pref("dom.disable_open_during_load", false);
  user_pref("dom.max_script_run_time", 0);
  ''';
  
        final Directory temporaryProfileDirectory = Directory(
            path.join(environment.webUiDartToolDir.path, 'firefox_profile'));
  
        // A good source of various Firefox Command Line options:
        // https://developer.mozilla.org/en-US/docs/Mozilla/Command_Line_Options#Browser
        //
        if (temporaryProfileDirectory.existsSync()) {
          temporaryProfileDirectory.deleteSync();
        }
        temporaryProfileDirectory.createSync(recursive: true);
  
        File(path.join(temporaryProfileDirectory.path, 'prefs.js'))
            .writeAsStringSync(_profile);
        bool isMac = Platform.isMacOS;
        var args = [
          url.toString(),
          '--profile',
          '${temporaryProfileDirectory.path}',
          '--headless',
          '-width $kMaxScreenshotWidth',
          '-height $kMaxScreenshotHeight',
  