Use new downcast helper for blink::HTMLFrameElement

This CL has goal to use IsA<HTMLFrameElement>(element) in place of
IsHTMLFrameElement(element)

Bug: 891908
Change-Id: I97f4bd55fa1145bf70dbe776afb419e2fbd96822
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1930538Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Abhijeet | Igalia <abhijeet@igalia.com>
Cr-Commit-Position: refs/heads/master@{#718990}

third_party/blink/renderer/modules/accessibility/ax_node_object.cc

@@ -819,7 +819,7 @@ ax::mojom::Role AXNodeObject::NativeRoleIgnoringAria() const {
     return ax::mojom::Role::kIgnored;
 
   // Treat <iframe> and <frame> the same.
-  if (IsA<HTMLIFrameElement>(*GetNode()) || IsHTMLFrameElement(*GetNode())) {
+  if (IsA<HTMLIFrameElement>(*GetNode()) || IsA<HTMLFrameElement>(*GetNode())) {
     const AtomicString& aria_role =
         GetAOMPropertyOrARIAAttribute(AOMStringProperty::kRole);
     if (aria_role == "none" || aria_role == "presentation")