anchor.diff:  class BrowserTestRunner {
     static const int MAX_NEXT_TEST_TIMEOUTS = 10;
     static const Duration NEXT_TEST_TIMEOUT = const Duration(seconds: 60);
  +  static const Duration RESTART_BROWSER_INTERVAL = const Duration(seconds: 60);
   
     final Map globalConfiguration;
     final bool checkedMode; // needed for dartium
  
positive.code: 
      // We are currently terminating this browser, don't start a new test.
      if (status.timeout) return null;
  
      BrowserTest test = testQueue.removeLast();
      if (status.currentTest == null) {
  
negative.code:               var status = new BrowserTestingStatus(browser);
                browserStatus[browser.id] = status;
                status.nextTestTimeout = createNextTestTimer(status);
                status.timeSinceRestart.start();
              }
              return success;
            });
  