Move NoEventDispatchAssertion class to its own file

Source/core/events/EventDispatcher.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2011 Google 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.
  *
  * 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.
  */
 
 #include "config.h"
 #include "core/events/EventDispatcher.h"
 
 #include "core/dom/ContainerNode.h"
+#include "core/dom/NoEventDispatchAssertion.h"
 #include "core/events/EventDispatchMediator.h"
 #include "core/events/MouseEvent.h"
 #include "core/events/ScopedEventQueue.h"
 #include "core/events/WindowEventContext.h"
 #include "core/frame/FrameView.h"
 #include "core/inspector/InspectorInstrumentation.h"
 #include "core/inspector/InspectorTraceEvents.h"
 #include "platform/TraceEvent.h"
 #include "wtf/RefPtr.h"
 
@@ skipping 185 matching lines @@
         }
     }
 }
 
 const NodeEventContext* EventDispatcher::topNodeEventContext()
 {
     return m_event->eventPath().isEmpty() ? 0 : &m_event->eventPath().last();
 }
 
 }