Minimal feature collector for select selectors.

Source/core/dom/shadow/SelectRuleFeatureSet.cpp

Index: Source/core/dom/shadow/SelectRuleFeatureSet.cpp
diff --git a/Source/core/dom/shadow/SelectRuleFeatureSet.cpp b/Source/core/dom/shadow/SelectRuleFeatureSet.cpp
index 23338960589a0e32cc2b31bf1bda67683d39220f..40a398e5502a2ce4fd096b8c6bf87f3b1b64045d 100644
--- a/Source/core/dom/shadow/SelectRuleFeatureSet.cpp
+++ b/Source/core/dom/shadow/SelectRuleFeatureSet.cpp
@@ -32,11 +32,26 @@
 #include "core/dom/shadow/SelectRuleFeatureSet.h"
 
 #include "core/css/CSSSelector.h"
+#include "core/css/CSSSelectorList.h"
 
 #include "wtf/BitVector.h"
 
 namespace blink {
 
+void SelectRuleFeatureSet::collectFeaturesFromSelector(const CSSSelector& selector)
+{
+    for (const CSSSelector* current = &selector; current; current = current->tagHistory()) {
+        if (invalidationSetForSelector(*current))
+            continue;
+
+        if (!current->selectorList())
+            continue;
+
+        for (const CSSSelector* selector = current->selectorList()->first(); selector; selector = CSSSelectorList::next(*selector))
+            collectFeaturesFromSelector(*selector);
+    }
+}
+
 bool SelectRuleFeatureSet::checkSelectorsForClassChange(const SpaceSplitString& changedClasses) const
 {
     unsigned changedSize = changedClasses.size();