Port 1551320 - Replace all CreateElement calls in XUL documents with CreateXULElement. r=mossop

lib/CFRPageActions.jsm

@@ -291,7 +291,7 @@ class PageAction {
   }
 
   _createElementAndAppend({type, id}, parent) {
-    let element = this.window.document.createElement(type);
+    let element = this.window.document.createXULElement(type);
     if (id) {
       element.setAttribute("id", id);
     }
@@ -397,7 +397,7 @@ class PageAction {
         stepsContainer.remove();
         stepsContainer = stepsContainer.cloneNode(false);
       } else {
-        stepsContainer = this.window.document.createElement("vbox");
+        stepsContainer = this.window.document.createXULElement("vbox");
         stepsContainer.setAttribute("id", stepsContainerId);
       }
       footerText.parentNode.appendChild(stepsContainer);

test/unit/asrouter/CFRPageActions.test.js

@@ -64,6 +64,7 @@ describe("CFRPageActions", () => {
       PrivateBrowsingUtils: {isWindowPrivate: sandbox.stub().returns(false)},
       gBrowser: {selectedBrowser: fakeBrowser},
     });
+    document.createXULElement = document.createElement;
 
     elements = {};
     const [body] = document.getElementsByTagName("body");