Collect active stylesheets and and apply asynchronously.

third_party/WebKit/Source/core/css/StyleSheetContents.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 599 matching lines @@
 
 RuleSet& StyleSheetContents::ensureRuleSet(const MediaQueryEvaluator& medium,
                                            AddRuleFlags addRuleFlags) {
   if (!m_ruleSet) {
     m_ruleSet = RuleSet::create();
     m_ruleSet->addRulesFromSheet(this, medium, addRuleFlags);
   }
   return *m_ruleSet.get();
 }
 
-static void clearResolvers(HeapHashSet<WeakMember<CSSStyleSheet>>& clients) {
+static void setNeedsActiveStyleUpdateForClients(
+    HeapHashSet<WeakMember<CSSStyleSheet>>& clients) {
   for (const auto& sheet : clients) {
-    if (Document* document = sheet->ownerDocument())
-      document->styleEngine().clearResolver();
+    Document* document = sheet->ownerDocument();
+    Node* node = sheet->ownerNode();
+    if (!document || !node || !node->isConnected())
+      continue;
+    document->styleEngine().setNeedsActiveStyleUpdate(node->treeScope());
   }
 }
 
 void StyleSheetContents::clearRuleSet() {
   if (StyleSheetContents* parentSheet = parentStyleSheet())
     parentSheet->clearRuleSet();
 
-  // Don't want to clear the StyleResolver if the RuleSet hasn't been created
-  // since we only clear the StyleResolver so that it's members are properly
-  // updated in ScopedStyleResolver::addRulesFromSheet.
   if (!m_ruleSet)
     return;
 
-  // Clearing the ruleSet means we need to recreate the styleResolver data
-  // structures. See the StyleResolver calls in
-  // ScopedStyleResolver::addRulesFromSheet.
-  clearResolvers(m_loadingClients);
-  clearResolvers(m_completedClients);
   m_ruleSet.clear();
+  setNeedsActiveStyleUpdateForClients(m_loadingClients);
+  setNeedsActiveStyleUpdateForClients(m_completedClients);
 }
 
 static void removeFontFaceRules(HeapHashSet<WeakMember<CSSStyleSheet>>& clients,
                                 const StyleRuleFontFace* fontFaceRule) {
   for (const auto& sheet : clients) {
     if (Node* ownerNode = sheet->ownerNode())
       ownerNode->document().styleEngine().removeFontFaceRules(
           HeapVector<Member<const StyleRuleFontFace>>(1, fontFaceRule));
   }
 }
@@ skipping 38 matching lines @@
   visitor->trace(m_importRules);
   visitor->trace(m_namespaceRules);
   visitor->trace(m_childRules);
   visitor->trace(m_loadingClients);
   visitor->trace(m_completedClients);
   visitor->trace(m_ruleSet);
   visitor->trace(m_referencedFromResource);
 }
 
 }  // namespace blink