Noissue - Throw an error if the client code doesn't load

test/browser/elemHideEmulation.js

Index: test/browser/elemHideEmulation.js
===================================================================
--- a/test/browser/elemHideEmulation.js
+++ b/test/browser/elemHideEmulation.js
@@ -89,27 +89,30 @@
 }
 
 function createPseudoElementWithStyle(element, pseudo, styleBlock)
 {
   insertStyleRule(`#${element.id}${pseudo} ${styleBlock}`);
 }
 
 // Will ensure the class ElemHideEmulation is loaded.
-// NOTE: if it never loads, this will probably hang.
-function loadElemHideEmulation()
+// Pass true when it calls itself.
+function loadElemHideEmulation(inside)
 {
   if (typeof ElemHideEmulation == "undefined")
   {
+    if (inside)
+      return Promise.reject("Failed to load ElemHideEmulation.");
+
     return loadScript(myUrl + "/../../../lib/common.js").then(() =>
     {
       return loadScript(myUrl + "/../../../chrome/content/elemHideEmulation.js");
     }).then(() =>
     {
-      return loadElemHideEmulation();
+      return loadElemHideEmulation(true);
     });
   }
 
   return Promise.resolve();
 }
 
 // Create a new ElemHideEmulation instance with @selectors.
 function applyElemHideEmulation(selectors)