Avoid leaking ThreadingPrimitives.h from StackStats.h when collection is off.

Source/core/rendering/RenderListItem.cpp

 /**
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Andrew Wellington (proton@wiretapped.net)
  *
  * 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 284 matching lines @@
             m_marker->updateMarginsAndContent();
             // If markerParent is an anonymous block that has lost all its children, destroy it.
             if (markerParent && markerParent->isAnonymousBlock() && !markerParent->firstChild() && !toRenderBlock(markerParent)->continuation())
                 markerParent->destroy();
         }
     }
 }
 
 void RenderListItem::layout()
 {
-    StackStats::LayoutCheckPoint layoutCheckPoint;
     ASSERT(needsLayout());
 
     updateMarkerLocation();
     RenderBlock::layout();
 }
 
 void RenderListItem::addOverflowFromChildren()
 {
     RenderBlock::addOverflowFromChildren();
     positionListMarker();
@@ skipping 189 matching lines @@
             // assume that all the following ones have too.
             // This gives us the opportunity to stop here and avoid
             // marking the same nodes again.
             break;
         }
         item->updateValue();
     }
 }
 
 } // namespace WebCore