Bug 1820634 - Fix assert that triggers in 380217-1.xhtml.

MANUAL PUSH: Trivial orange fix CLOSED TREE

layout/generic/CSSOrderAwareFrameIterator.cpp

@@ -11,8 +11,8 @@
 
 static bool CanUse(const nsIFrame* aFrame) {
   return aFrame->IsFlexOrGridContainer() || aFrame->IsXULBoxFrame() ||
-         (aFrame->GetContent() &&
-          aFrame->GetContent()->IsXULElement(nsGkAtoms::treecols));
+         (aFrame->GetContent() && aFrame->GetContent()->IsAnyOfXULElements(
+                                      nsGkAtoms::treecols, nsGkAtoms::treecol));
 }
 
 namespace mozilla {