CSS: Avoid invalidating style when only descendants need updating

Source/core/css/RuleFeature.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 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 300 matching lines @@
 
     if (!contentValue->isValueList())
         return;
 
     for (auto& item : toCSSValueList(*contentValue)) {
         if (!item->isFunctionValue())
             continue;
         CSSFunctionValue* functionValue = toCSSFunctionValue(item.get());
         if (functionValue->functionType() != CSSValueAttr)
             continue;
-        ensureAttributeInvalidationSet(AtomicString(toCSSPrimitiveValue(functionValue->item(0))->getStringValue()));
+        ensureAttributeInvalidationSet(AtomicString(toCSSPrimitiveValue(functionValue->item(0))->getStringValue())).setInvalidatesSelf();
     }
 }
 
 std::pair<const CSSSelector*, RuleFeatureSet::UseFeaturesType>
 RuleFeatureSet::extractInvalidationSetFeatures(const CSSSelector& selector, InvalidationSetFeatures& features, bool negated)
 {
     bool foundFeatures = false;
     for (const CSSSelector* current = &selector; current; current = current->tagHistory()) {
         if (!negated)
             foundFeatures |= extractInvalidationSetFeature(*current, features);
         // Initialize the entry in the invalidation set map, if supported.
-        if (!invalidationSetForSelector(*current)) {
+        if (InvalidationSet* invalidationSet = invalidationSetForSelector(*current)) {
+            invalidationSet->setInvalidatesSelf();
+        } else {
             if (requiresSubtreeInvalidation(*current)) {
                 // Fall back to use subtree invalidations, even for features in the
                 // rightmost compound selector. Returning the start &selector here
                 // will make addFeaturesToInvalidationSets start marking invalidation
                 // sets for subtree recalc for features in the rightmost compound
                 // selector.
                 return std::make_pair(&selector, ForceSubtree);
             }
             if (const CSSSelectorList* selectorList = current->selectorList()) {
                 ASSERT(supportsInvalidationWithSelectorList(current->pseudoType()));
@@ skipping 241 matching lines @@
     visitor->trace(siblingRules);
     visitor->trace(uncommonAttributeRules);
     visitor->trace(m_classInvalidationSets);
     visitor->trace(m_attributeInvalidationSets);
     visitor->trace(m_idInvalidationSets);
     visitor->trace(m_pseudoInvalidationSets);
 #endif
 }
 
 } // namespace blink