Use LocalStyleChange for content:attr() changes.

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 319 matching lines @@
         case CSSSelector::DirectAdjacent:
         case CSSSelector::IndirectAdjacent:
             features.wholeSubtree = true;
             break;
         }
     }
 }
 
 void RuleFeatureSet::addContentAttr(const AtomicString& attributeName)
 {
-    DescendantInvalidationSet& invalidationSet = ensureAttributeInvalidationSet(attributeName);
-    invalidationSet.setWholeSubtreeInvalid();
+    ensureAttributeInvalidationSet(attributeName);
 }
 
 void RuleFeatureSet::collectFeaturesFromRuleData(const RuleData& ruleData)
 {
     FeatureMetadata metadata;
     InvalidationSetMode mode = updateInvalidationSets(ruleData.selector());
 
     collectFeaturesFromSelector(ruleData.selector(), metadata, mode);
     m_metadata.add(metadata);
 
@@ skipping 211 matching lines @@
     visitor->trace(uncommonAttributeRules);
     visitor->trace(m_classInvalidationSets);
     visitor->trace(m_attributeInvalidationSets);
     visitor->trace(m_idInvalidationSets);
     visitor->trace(m_pseudoInvalidationSets);
     visitor->trace(m_styleInvalidator);
 #endif
 }
 
 } // namespace blink