increase browserDisconnectTimeout

packages/firestore/karma.conf.js

@@ -24,9 +24,10 @@ module.exports = function (config) {
     browsers: getTestBrowsers(argv),
     // files to load into karma
     files: getTestFiles(argv),
+    browserDisconnectTimeout: 5000,
 
     concurrency: 1,
-    
+
     preprocessors: {
       'test/**/*.ts': ['webpack', 'sourcemap']
     },