Add a first pass of a class descendant invalidator, and a containing RuleSetAnalyzer

Source/core/css/RuleFeature.cpp

Index: Source/core/css/RuleFeature.cpp
diff --git a/Source/core/css/RuleFeature.cpp b/Source/core/css/RuleFeature.cpp
index 7c8f160ae43f4d7445289aeda1ee292c72301f55..f693b844c944a704df05b6252e5f4f6aa7efe941 100644
--- a/Source/core/css/RuleFeature.cpp
+++ b/Source/core/css/RuleFeature.cpp
@@ -69,6 +69,9 @@ void RuleFeatureSet::collectFeaturesFromSelectorList(const CSSSelectorList* sele
 
 void RuleFeatureSet::add(const RuleFeatureSet& other)
 {
+    if (const RuleSetAnalyzer* otherAnalyzer = other.getRuleSetAnalyzer())
+        ensureRuleSetAnalyzer()->combine(*otherAnalyzer);
+
     HashSet<AtomicString>::const_iterator end = other.idsInRules.end();
     for (HashSet<AtomicString>::const_iterator it = other.idsInRules.begin(); it != end; ++it)
         idsInRules.add(*it);
@@ -95,4 +98,16 @@ void RuleFeatureSet::clear()
     m_maxDirectAdjacentSelectors = 0;
 }
 
+const RuleSetAnalyzer* RuleFeatureSet::getRuleSetAnalyzer() const
+{
+    return ruleSetAnalyzer.get();
+}
+
+RuleSetAnalyzer* RuleFeatureSet::ensureRuleSetAnalyzer()
+{
+    if (!ruleSetAnalyzer)
+        ruleSetAnalyzer = RuleSetAnalyzer::create();
+    return ruleSetAnalyzer.get();
+}
+
 } // namespace WebCore