Include Event.h in fewer header files

Source/core/dom/ExecutionContext.h

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2012 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 14 matching lines @@
  *
  */
 
 #ifndef ExecutionContext_h
 #define ExecutionContext_h
 
 #include "core/dom/ActiveDOMObject.h"
 #include "core/dom/ExecutionContextClient.h"
 #include "core/dom/SandboxFlags.h"
 #include "core/dom/SecurityContext.h"
-#include "core/events/ErrorEvent.h"
 #include "core/fetch/CrossOriginAccessControl.h"
 #include "core/frame/ConsoleTypes.h"
 #include "core/frame/DOMTimer.h"
 #include "platform/LifecycleContext.h"
 #include "platform/Supplementable.h"
 #include "platform/heap/Handle.h"
 #include "platform/weborigin/KURL.h"
 #include "wtf/Functional.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace WTF {
 class OrdinalNumber;
 }
 
 namespace WebCore {
 
 class ContextLifecycleNotifier;
 class LocalDOMWindow;
+class ErrorEvent;
 class EventListener;
 class EventQueue;
 class EventTarget;
 class ExecutionContextTask;
 class ScriptState;
 class PublicURLManager;
 class SecurityOrigin;
 class ScriptCallStack;
 
 class ExecutionContext
@@ skipping 112 matching lines @@
 
     // The location of this member is important; to make sure contextDestroyed() notification on
     // ExecutionContext's members (notably m_timeouts) is called before they are destructed,
     // m_lifecycleNotifer should be placed *after* such members.
     OwnPtr<ContextLifecycleNotifier> m_lifecycleNotifier;
 };
 
 } // namespace WebCore
 
 #endif // ExecutionContext_h