Don't include LayoutObject-derived headers where not needed.

third_party/WebKit/Source/modules/accessibility/AXObject.cpp

 /*
  * Copyright (C) 2008, 2009, 2011 Apple 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 21 matching lines @@
 #include "core/css/resolver/StyleResolver.h"
 #include "core/dom/DocumentUserGestureToken.h"
 #include "core/editing/EditingUtilities.h"
 #include "core/editing/VisibleUnits.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/html/HTMLDialogElement.h"
 #include "core/html/HTMLFrameOwnerElement.h"
 #include "core/html/parser/HTMLParserIdioms.h"
-#include "core/layout/LayoutBox.h"
+#include "core/layout/LayoutBoxModelObject.h"
 #include "modules/accessibility/AXObjectCacheImpl.h"
 #include "platform/UserGestureIndicator.h"
 #include "platform/text/PlatformLocale.h"
 #include "wtf/HashSet.h"
 #include "wtf/StdLibExtras.h"
 #include "wtf/text/WTFString.h"
 
 using blink::WebLocalizedString;
 
 namespace blink {
@@ skipping 1689 matching lines @@
 }
 
 DEFINE_TRACE(AXObject) {
   visitor->trace(m_children);
   visitor->trace(m_parent);
   visitor->trace(m_cachedLiveRegionRoot);
   visitor->trace(m_axObjectCache);
 }
 
 }  // namespace blink