Bug 1387023 - initialize devtools before asserting menu items in browser_989751_subviewbutton_class.js;r=Gijs

MozReview-Commit-ID: 9piucVkS0Y9

--HG--
extra : rebase_source : bea3a2a6c02fa7689b0b2437567dfb91d03701a0

browser/components/customizableui/test/browser_989751_subviewbutton_class.js

@@ -15,6 +15,11 @@ function insertClassNameToMenuChildren(parentMenu) {
 
 function checkSubviewButtonClass(menuId, buttonId, subviewId) {
   return async function() {
+    // Initialize DevTools before starting the test in order to create menuitems in
+    // menuWebDeveloperPopup.
+    Cu.import("resource://devtools/shared/Loader.jsm", {})
+        .require("devtools/client/framework/devtools-browser");
+
     info("Checking for items without the subviewbutton class in " + buttonId + " widget");
     let menu = document.getElementById(menuId);
     insertClassNameToMenuChildren(menu);