chore(runner): make plugins optional param for createBrowser

Author: sjelin

Diff for: lib/runner.js

@@ -172,6 +172,8 @@ Runner.prototype.setupGlobals_ = function(browser_) {
  * This is used to set up the initial protractor instances and any
  * future ones.
  *
+ * @param {?Plugin} The plugin functions
+ *
  * @return {Protractor} a protractor instance.
  * @public
  */
@@ -183,7 +185,9 @@ Runner.prototype.createBrowser = function(plugins) {
       config.baseUrl, config.rootElement);
 
   browser_.params = config.params;
-  browser_.plugins_ = plugins;
+  if (plugins) {
+    browser_.plugins_ = plugins;
+  }
   if (config.getPageTimeout) {
     browser_.getPageTimeout = config.getPageTimeout;
   }