EventSender<T> singletons are better off on the Oilpan heap.

third_party/WebKit/Source/core/html/HTMLDetailsElement.h

 /*
  * Copyright (C) 2010, 2011 Nokia Corporation and/or its subsidiary(-ies)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #ifndef HTMLDetailsElement_h
 #define HTMLDetailsElement_h
 
 #include "core/html/HTMLElement.h"
 
 namespace blink {
 
 template<typename T> class EventSender;
-typedef EventSender<HTMLDetailsElement> DetailsEventSender;
+using DetailsEventSender = EventSender<HTMLDetailsElement>;
 
 class HTMLDetailsElement final : public HTMLElement {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static PassRefPtrWillBeRawPtr<HTMLDetailsElement> create(Document&);
     void toggleOpen();
     ~HTMLDetailsElement() override;
 
     void dispatchPendingEvent(DetailsEventSender*);
 
     Element* findMainSummary() const;
 
 private:
     explicit HTMLDetailsElement(Document&);
 
     LayoutObject* createLayoutObject(const ComputedStyle&) override;
     void parseAttribute(const QualifiedName&, const AtomicString&, const AtomicString&) override;
     void didAddUserAgentShadowRoot(ShadowRoot&) override;
     bool isInteractiveContent() const override;
 
     bool m_isOpen;
 };
 
 } // namespace blink
 
 #endif // HTMLDetailsElement_h