StyleResolver should update RuleSets lazily.

Source/core/dom/Element.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 974 matching lines @@
     } else if (isStyledElement() && isPresentationAttribute(name)) {
         elementData()->m_presentationAttributeStyleIsDirty = true;
         setNeedsStyleRecalc(LocalStyleChange);
     }
 
     if (isIdAttributeName(name)) {
         AtomicString oldId = elementData()->idForStyleResolution();
         AtomicString newId = makeIdForStyleResolution(newValue, document().inQuirksMode());
         if (newId != oldId) {
             elementData()->setIdForStyleResolution(newId);
-            shouldInvalidateStyle = testShouldInvalidateStyle && checkNeedsStyleInvalidationForIdChange(oldId, newId, styleResolver->ruleFeatureSet());
+            shouldInvalidateStyle = testShouldInvalidateStyle && checkNeedsStyleInvalidationForIdChange(oldId, newId, styleResolver->ensureRuleFeatureSet());
         }
     } else if (name == classAttr) {
         classAttributeChanged(newValue);
     } else if (name == HTMLNames::nameAttr) {
         setHasName(!newValue.isNull());
     } else if (name == HTMLNames::pseudoAttr) {
         shouldInvalidateStyle |= testShouldInvalidateStyle && isInShadowTree();
     }
 
     invalidateNodeListCachesInAncestors(&name, this);
@@ skipping 94 matching lines @@
 {
     StyleResolver* styleResolver = document().styleResolverIfExists();
     bool testShouldInvalidateStyle = inActiveDocument() && styleResolver && styleChangeType() < SubtreeStyleChange;
     bool shouldInvalidateStyle = false;
 
     if (classStringHasClassName(newClassString)) {
         const bool shouldFoldCase = document().inQuirksMode();
         const SpaceSplitString oldClasses = elementData()->classNames();
         elementData()->setClass(newClassString, shouldFoldCase);
         const SpaceSplitString& newClasses = elementData()->classNames();
-        shouldInvalidateStyle = testShouldInvalidateStyle && checkSelectorForClassChange(oldClasses, newClasses, styleResolver->ruleFeatureSet());
+        shouldInvalidateStyle = testShouldInvalidateStyle && checkSelectorForClassChange(oldClasses, newClasses, styleResolver->ensureRuleFeatureSet());
     } else {
         const SpaceSplitString& oldClasses = elementData()->classNames();
-        shouldInvalidateStyle = testShouldInvalidateStyle && checkSelectorForClassChange(oldClasses, styleResolver->ruleFeatureSet());
+        shouldInvalidateStyle = testShouldInvalidateStyle && checkSelectorForClassChange(oldClasses, styleResolver->ensureRuleFeatureSet());
         elementData()->clearClass();
     }
 
     if (hasRareData())
         elementRareData()->clearClassListValueForQuirksMode();
 
     if (shouldInvalidateStyle)
         setNeedsStyleRecalc();
 }
 
@@ skipping 1865 matching lines @@
         return;
 
     if (!oldForAttributeValue.isEmpty())
         scope.removeLabel(oldForAttributeValue, toHTMLLabelElement(this));
     if (!newForAttributeValue.isEmpty())
         scope.addLabel(newForAttributeValue, toHTMLLabelElement(this));
 }
 
 static bool hasSelectorForAttribute(Document* document, const AtomicString& localName)
 {
-    return document->styleResolver() && document->styleResolver()->ruleFeatureSet().hasSelectorForAttribute(localName);
+    return document->styleResolver() && document->styleResolver()->ensureRuleFeatureSet().hasSelectorForAttribute(localName);
 }
 
 void Element::willModifyAttribute(const QualifiedName& name, const AtomicString& oldValue, const AtomicString& newValue)
 {
     if (isIdAttributeName(name))
         updateId(oldValue, newValue);
     else if (name == HTMLNames::nameAttr)
         updateName(oldValue, newValue);
     else if (name == HTMLNames::forAttr && hasTagName(labelTag)) {
         TreeScope& scope = treeScope();
@@ skipping 507 matching lines @@
     // Before doing so, we need to resolve issues in HTMLSelectElement::recalcListItems
     // and RenderMenuList::setText. See also https://bugs.webkit.org/show_bug.cgi?id=88405
     if (hasTagName(optionTag) || hasTagName(optgroupTag))
         return false;
     if (FullscreenElementStack::isActiveFullScreenElement(this))
         return false;
     return true;
 }
 
 } // namespace WebCore