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

Source/core/rendering/RenderBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. 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
@@ skipping 365 matching lines @@
             setHasOverflowClip();
         }
     }
 
     setHasTransform(styleToUse->hasTransformRelatedProperty());
     setHasReflection(styleToUse->boxReflect());
 }
 
 void RenderBox::layout()
 {
-    StackStats::LayoutCheckPoint layoutCheckPoint;
     ASSERT(needsLayout());
 
     RenderObject* child = firstChild();
     if (!child) {
         clearNeedsLayout();
         return;
     }
 
     LayoutStateMaintainer statePusher(view(), this, locationOffset(), style()->isFlippedBlocksWritingMode());
     while (child) {
@@ skipping 4338 matching lines @@
     }
 
     if (didSplitParentAnonymousBoxes)
         markBoxForRelayoutAfterSplit(this);
 
     ASSERT(beforeChild->parent() == this);
     return beforeChild;
 }
 
 } // namespace WebCore