Clear m_treeBoundaryCrossingScopes when reconstructing StyleResolver.

third_party/WebKit/Source/core/dom/StyleEngine.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.
@@ skipping 437 matching lines @@
   // StyleEngine::shadowRootRemovedFromDocument removes not-in-document
   // treescopes from activeTreeScopes. StyleEngine::didRemoveShadowRoot
   // removes treescopes which are being destroyed from activeTreeScopes.
   // So we need to clearScopedStyleResolver for treescopes which have been
   // just removed from document. If document is destroyed before invoking
   // updateActiveStyleSheets, the treescope has a scopedStyleResolver which
   // has destroyed StyleSheetContents.
   for (TreeScope* treeScope : m_activeTreeScopes)
     treeScope->clearScopedStyleResolver();
 
+  m_treeBoundaryCrossingScopes.clear();
+
   if (m_resolver) {
     TRACE_EVENT1("blink", "StyleEngine::clearResolver", "frame",
                  document().frame());
     m_resolver->dispose();
     m_resolver.clear();
   }
 }
 
 void StyleEngine::clearMasterResolver() {
   if (Document* master = this->master())
@@ skipping 550 matching lines @@
 }
 
 DEFINE_TRACE_WRAPPERS(StyleEngine) {
   for (auto sheet : m_injectedAuthorStyleSheets) {
     visitor->traceWrappers(sheet);
   }
   visitor->traceWrappers(m_documentStyleSheetCollection);
 }
 
 }  // namespace blink