Clear active tree scopes on StyleEngine::didDetach().

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 408 matching lines @@
   if (m_document->getSecurityOrigin()->canRequest(sheet.baseURL()))
     addRuleFlags = RuleHasDocumentSecurityOrigin;
   return &sheet.contents()->ensureRuleSet(*m_mediaQueryEvaluator, addRuleFlags);
 }
 
 void StyleEngine::createResolver() {
   m_resolver = StyleResolver::create(*m_document);
   m_resolver->setRuleUsageTracker(m_tracker);
 }
 
-void StyleEngine::clearResolver() {
+void StyleEngine::clearResolvers() {
   DCHECK(!document().inStyleRecalc());
   DCHECK(isMaster() || !m_resolver);
 
   document().clearScopedStyleResolver();
-  // TODO(rune@opera.com): The clearing of all shadow tree scoped style
-  // resolvers below should not be necessary. It was introduced to fix a crash
-  // bug (https://crbug.com/447976) when clearResolver is called from didDetach
-  // on document destruction. That was pre-oilpan, and removing the for-loop
-  // below does not re-introduce that crash. If m_activeTreeScopes keeps too
-  // much memory alive after detach, we should probably clear m_activeTreeScopes
-  // in didDetach instead.
-  //
-  // The current code will clear too much if clearResolver is called from
-  // clearMasterResolver as a result of a Reconstruct in
-  // DocumentStyleSheetCollection. Such a reconstruct should not necessarily
-  // affect scoped resolvers from shadow trees at all.
   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::didDetach() {
+  clearResolvers();
   m_globalRuleSet.dispose();
-  clearResolver();
+  m_treeBoundaryCrossingScopes.clear();
+  m_dirtyTreeScopes.clear();
+  m_activeTreeScopes.clear();
   m_viewportResolver = nullptr;
   m_mediaQueryEvaluator = nullptr;
   clearFontCache();
 }
 
 void StyleEngine::clearFontCache() {
   if (m_fontSelector)
     m_fontSelector->fontFaceCache()->clearCSSConnected();
   if (m_resolver)
     m_resolver->invalidateMatchedPropertiesCache();
@@ skipping 670 matching lines @@
 }
 
 DEFINE_TRACE_WRAPPERS(StyleEngine) {
   for (auto sheet : m_injectedAuthorStyleSheets) {
     visitor->traceWrappers(sheet);
   }
   visitor->traceWrappers(m_documentStyleSheetCollection);
 }
 
 }  // namespace blink