ScopedStyleResolver should be cleared when ShadowRoot is removed from document.

Source/core/css/resolver/StyleResolver.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 236 matching lines @@
         const WillBeHeapVector<RawPtrWillBeMember<StyleRuleFontFace> > fontFaceRules = authorRules.fontFaceRules();
         for (unsigned i = 0; i < fontFaceRules.size(); ++i)
             addFontFaceRule(m_document, document().styleEngine()->fontSelector(), fontFaceRules[i]);
         if (fontFaceRules.size())
             invalidateMatchedPropertiesCache();
     }
 }
 
 void StyleResolver::resetAuthorStyle(TreeScope& treeScope)
 {
+    m_treeBoundaryCrossingRules.reset(&treeScope.rootNode());
+    resetRuleFeatures();
+
     ScopedStyleResolver* resolver = treeScope.scopedStyleResolver();
     if (!resolver)
         return;
 
-    m_treeBoundaryCrossingRules.reset(&treeScope.rootNode());
     resolver->resetAuthorStyle();
-    resetRuleFeatures();
     if (treeScope.rootNode().isDocumentNode())
         return;
 
     // resolver is going to be freed below.
     treeScope.clearScopedStyleResolver();
 }
 
 static PassOwnPtrWillBeRawPtr<RuleSet> makeRuleSet(const WillBeHeapVector<RuleFeature>& rules)
 {
     size_t size = rules.size();
@@ skipping 1328 matching lines @@
     visitor->trace(m_uncommonAttributeRuleSet);
     visitor->trace(m_watchedSelectorsRules);
     visitor->trace(m_treeBoundaryCrossingRules);
     visitor->trace(m_styleSharingLists);
     visitor->trace(m_pendingStyleSheets);
     visitor->trace(m_document);
 #endif
 }
 
 } // namespace blink