MAGETWO-87898: Stabilize tests

Author: kieuphan2406

dev/tests/acceptance/tests/functional/Magento/FunctionalTest/Banner/Test/AdminPageBuilderEnabledTest.xml

@@ -78,7 +78,7 @@
         </actionGroup>
         <seeElement selector="{{TinyMCESection.TinyMCE4}}" stepKey="seeTinyMCE4Visible" />
         <!--Missing step of asserting PageBuilder text convert to TinyMCE4 (blocked by current testing framework - unable to grab text from TinyMCE4)-->
-        <executeJS function="var div = document.createElement('div'); div.innerHTML = tinymce.activeEditor.getContent(); div.innerText.trim();" stepKey="textFromPageBuilder"/>
+        <executeJS function="return (function() {var div = document.createElement('div'); div.innerHTML = tinymce.activeEditor.getContent(); return div.innerText.trim();}())" stepKey="textFromPageBuilder"/>
         <assertEquals stepKey="assertEquals1" message="pass">
             <expectedResult type="string">Hello Dynamic Block from PageBuilder</expectedResult>
             <actualResult type="variable">textFromPageBuilder</actualResult>