Backed out 3 changesets (bug 1638153) for perma failures on cross-origin-objects.html. CLOSED TREE

Backed out changeset f7aedc92d396 (bug 1638153)
Backed out changeset 07ec713926c6 (bug 1638153)
Backed out changeset 5a656842e241 (bug 1638153)

browser/base/content/sanitizeDialog.js

@@ -57,7 +57,9 @@ var gSanitizePromptDialog = {
         .translateFragment(warningDesc)
         .then(() => {
           // And then ensure we've run layout.
-          let rootWin = window.browsingContext.topChromeWindow;
+          let rootWin = window.docShell.rootTreeItem.QueryInterface(
+            Ci.nsIDocShell
+          ).domWindow;
           return rootWin.promiseDocumentFlushed(() => {});
         });
     } else {