Avoid always style recalc when removing stylesheets.

Source/core/css/resolver/ScopedStyleResolver.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 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.
@@ skipping 82 matching lines @@
     typedef HashMap<const StringImpl*, RefPtr<StyleRuleKeyframes> > KeyframesRuleMap;
     KeyframesRuleMap m_keyframesRuleMap;
 };
 
 class ScopedStyleTree {
     WTF_MAKE_NONCOPYABLE(ScopedStyleTree); WTF_MAKE_FAST_ALLOCATED;
 public:
     ScopedStyleTree() : m_scopedResolverForDocument(0), m_buildInDocumentOrder(true) { }
 
     ScopedStyleResolver* ensureScopedStyleResolver(const ContainerNode& scopingNode);
+    ScopedStyleResolver* lookupScopedStyleResolverFor(const ContainerNode* scopingNode)
+    {
+        HashMap<const ContainerNode*, OwnPtr<ScopedStyleResolver> >::iterator it = m_authorStyles.find(scopingNode);
+        return it != m_authorStyles.end() ? it->value.get() : 0;
+    }
+
     ScopedStyleResolver* scopedStyleResolverFor(const ContainerNode& scopingNode);
     ScopedStyleResolver* addScopedStyleResolver(const ContainerNode& scopingNode, bool& isNewEntry);
     void clear();
 
     // for fast-path.
     bool hasOnlyScopedResolverForDocument() const { return m_scopedResolverForDocument && m_authorStyles.size() == 1; }
     ScopedStyleResolver* scopedStyleResolverForDocument() { return m_scopedResolverForDocument; }
 
     void resolveScopedStyles(const Element*, Vector<ScopedStyleResolver*, 8>&);
     void collectScopedResolversForHostedShadowTrees(const Element*, Vector<ScopedStyleResolver*, 8>&);
@@ skipping 40 matching lines @@
 {
     if (!cacheIsValid(element))
         resolveStyleCache(element);
 
     return m_cache.scopedResolver;
 }
 
 } // namespace WebCore
 
 #endif // ScopedStyleResolver_h