Remove PlatformEvent it is no longer used.

third_party/WebKit/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
@@ skipping 62 matching lines @@
   const String& code() const { return m_code; }
   const String& key() const { return m_key; }
 
   unsigned location() const { return m_location; }
 
   const WebKeyboardEvent* keyEvent() const { return m_keyEvent.get(); }
 
   int keyCode()
       const;  // key code for keydown and keyup, character for keypress
   int charCode() const;  // character code for keypress, 0 for keydown and keyup
-  bool repeat() const { return modifiers() & PlatformEvent::IsAutoRepeat; }
+  bool repeat() const { return modifiers() & WebInputEvent::IsAutoRepeat; }
 
   const AtomicString& interfaceName() const override;
   bool isKeyboardEvent() const override;
   int which() const override;
   bool isComposing() const { return m_isComposing; }
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
   KeyboardEvent();
   KeyboardEvent(const WebKeyboardEvent&, LocalDOMWindow*);
 
   void initLocationModifiers(unsigned location);
 
   std::unique_ptr<WebKeyboardEvent> m_keyEvent;
   String m_code;
   String m_key;
   unsigned m_location;
   bool m_isComposing;
 };
 
 DEFINE_EVENT_TYPE_CASTS(KeyboardEvent);
 
 }  // namespace blink
 
 #endif  // KeyboardEvent_h