Add use counter for indirect adjacent selectors.

third_party/WebKit/Source/core/css/parser/CSSSelectorParser.cpp

Index: third_party/WebKit/Source/core/css/parser/CSSSelectorParser.cpp
diff --git a/third_party/WebKit/Source/core/css/parser/CSSSelectorParser.cpp b/third_party/WebKit/Source/core/css/parser/CSSSelectorParser.cpp
index 08fe7fcb92577a9fcd56691b5b4ff187b3e682df..105b5e4ce2b4d49d6a6aedb5c3124d0316c28fe5 100644
--- a/third_party/WebKit/Source/core/css/parser/CSSSelectorParser.cpp
+++ b/third_party/WebKit/Source/core/css/parser/CSSSelectorParser.cpp
@@ -62,6 +62,8 @@ static void recordSelectorStats(const CSSParserContext& context, const CSSSelect
             }
             if (feature != UseCounter::NumberOfFeatures)
                 context.useCounter()->count(feature);
+            if (current->relation() == CSSSelector::IndirectAdjacent)
+                context.useCounter()->count(UseCounter::CSSSelectorIndirectAdjacent);
             if (current->selectorList())
                 recordSelectorStats(context, *current->selectorList());
         }