Implement PopupMenu::updateFromElement() for ExternalPopupMenu.

third_party/WebKit/Source/web/ExternalPopupMenu.h

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 60 matching lines @@
     void hide() override;
     void updateFromElement() override;
     void disconnectClient() override;
 
     // WebExternalPopupClient methods:
     void didChangeSelection(int index) override;
     void didAcceptIndex(int index) override;
     void didAcceptIndices(const WebVector<int>& indices) override;
     void didCancel() override;
 
+    bool showInternal();
     void dispatchEvent(Timer<ExternalPopupMenu>*);
+    void update();
 
     RawPtrWillBeMember<HTMLSelectElement> m_ownerElement;
     RefPtrWillBeMember<LocalFrame> m_localFrame;
     WebViewImpl& m_webView;
     OwnPtr<WebMouseEvent> m_syntheticEvent;
     Timer<ExternalPopupMenu> m_dispatchEventTimer;
     // The actual implementor of the show menu.
     WebExternalPopupMenu* m_webExternalPopupMenu;
+    uint64_t m_shownDOMTreeVersion = 0;
+    bool m_needsUpdate = false;
 };
 
 } // namespace blink
 
 #endif // ExternalPopupMenu_h