Avoid always style recalc when removing stylesheets.

Source/core/dom/StyleSheetScopingNodeList.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 33 matching lines @@
 
     if (m_scopingNodesRemoved)
         m_scopingNodesRemoved->remove(node);
 }
 
 void StyleSheetScopingNodeList::remove(ContainerNode* node)
 {
     if (isTreeScopeRoot(node) || !m_scopingNodes)
         return;
 
-    m_scopingNodes->remove(node);
+    // If the node is still working as a scoping node, we cannot remove.
     if (node->inDocument() && node->numberOfScopedHTMLStyleChildren())
         return;
 
+    m_scopingNodes->remove(node);
     if (!m_scopingNodesRemoved)
         m_scopingNodesRemoved = adoptPtr(new ListHashSet<Node*, 4>());
     m_scopingNodesRemoved->add(node);
 }
 
 }