Virtualize EventDispatchMediator creation and cleanup calling.

Source/core/events/KeyboardEvent.h

 /*
  * Copyright (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2001 Tobias Anton (anton@stud.fbi.fh-darmstadt.de)
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *
  * 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.
@@ skipping 70 matching lines @@
     const PlatformKeyboardEvent* keyEvent() const { return m_keyEvent.get(); }
 
     int keyCode() const override; // key code for keydown and keyup, character for keypress
     int charCode() const override; // character code for keypress, 0 for keydown and keyup
     bool repeat() const { return m_isAutoRepeat; }
 
     const AtomicString& interfaceName() const override;
     bool isKeyboardEvent() const override;
     int which() const override;
 
+    PassRefPtrWillBeRawPtr<EventDispatchMediator> createMediator() override;
+
     DECLARE_VIRTUAL_TRACE();
 
 private:
     KeyboardEvent();
     KeyboardEvent(const PlatformKeyboardEvent&, AbstractView*);
     KeyboardEvent(const AtomicString&, const KeyboardEventInit&);
     KeyboardEvent(const AtomicString& type, bool canBubble, bool cancelable, AbstractView*,
         const String& keyIdentifier, const String& code, const String& key, unsigned location,
         bool ctrlKey, bool altKey, bool shiftKey, bool metaKey);
 
@@ skipping 11 matching lines @@
 private:
     explicit KeyboardEventDispatchMediator(PassRefPtrWillBeRawPtr<KeyboardEvent>);
     bool dispatchEvent(EventDispatcher&) const override;
 };
 
 DEFINE_EVENT_TYPE_CASTS(KeyboardEvent);
 
 } // namespace blink
 
 #endif // KeyboardEvent_h