Add UseCounter for web components related CSS selectors

Source/core/css/parser/BisonCSSParser-in.cpp

Index: Source/core/css/parser/BisonCSSParser-in.cpp
diff --git a/Source/core/css/parser/BisonCSSParser-in.cpp b/Source/core/css/parser/BisonCSSParser-in.cpp
index d1b1f92b29efc92d2ada5787aeeea6288682e3ef..adc6b1b9a8f47670d47343d67d2cfbfeeb68b835 100644
--- a/Source/core/css/parser/BisonCSSParser-in.cpp
+++ b/Source/core/css/parser/BisonCSSParser-in.cpp
@@ -1761,6 +1761,35 @@ StyleRuleBase* BisonCSSParser::createStyleRule(Vector<OwnPtr<CSSParserSelector>
 {
     StyleRule* result = 0;
     if (selectors) {
+        for (size_t i = 0; i < selectors->size(); ++i) {

[esprehn, 2014/06/18 06:24:35]

Lets put this in another function and early return from m_context.useCounter().
If that's false you'll still loop through everything below and just do no
reporting so all the looping is wasted.

I also don't think you handle nested rules properly like :not(:host(...)).

[kochi, 2014/06/18 09:03:31]

Done.

Split the part into a separate function, and I noticed
that I do not have to use CSSParserSelector, instead
I should use CSSSelectorList.

Also addressed that :not(:host()) was not counted.

+            for (CSSParserSelector* selector = selectors->at(i).get(); selector; selector = selector->tagHistory()) {
+                UseCounter::Feature feature = UseCounter::NumberOfFeatures;
+                switch (selector->pseudoType()) {
+                case CSSSelector::PseudoUnresolved:
+                    feature = UseCounter::CSSSelectorPseudoUnresolved;
+                    break;
+                case CSSSelector::PseudoShadow:
+                    feature = UseCounter::CSSSelectorPseudoShadow;
+                    break;
+                case CSSSelector::PseudoContent:
+                    feature = UseCounter::CSSSelectorPseudoContent;
+                    break;
+                case CSSSelector::PseudoHost:
+                    feature = UseCounter::CSSSelectorPseudoHost;
+                    break;
+                case CSSSelector::PseudoHostContext:
+                    feature = UseCounter::CSSSelectorPseudoHostContext;
+                    break;
+                default:
+                    break;
+                }
+                if (selector->relation() == CSSSelector::ShadowDeep)
+                    feature = UseCounter::CSSDeepCombinator;
+                if (feature != UseCounter::NumberOfFeatures && m_context.useCounter())
+                    m_context.useCounter()->count(feature);
+            }
+        }
+
         m_allowImportRules = m_allowNamespaceDeclarations = false;
         RefPtrWillBeRawPtr<StyleRule> rule = StyleRule::create();
         rule->parserAdoptSelectorVector(*selectors);