fix(synchronizing): use the same control flow when ignoring sync

Previously, the order of frames and tasks on the control flow was
different depending on `browser.ignoreSynchronization`. This fixes
the inconsistency by creating an empty task when ignoreSynchronization
is true.

Practically, this fixes the polling spec failing after the update
to selenium-webdriver@2.47.0.

lib/protractor.js

@@ -320,7 +320,9 @@ Protractor.prototype.waitForAngular = function(opt_description) {
   var description = opt_description ? ' - ' + opt_description : '';
   var self = this;
   if (this.ignoreSynchronization) {
-    return webdriver.promise.fulfilled();
+    return self.driver.controlFlow().execute(function() {
+      return true;
+    }, 'Ignore Synchronization Protractor.waitForAngular()');
   }
 
   return this.executeAsyncScript_(