Add UseCounters for CSS-related *List interfaces with item() methods

Source/core/css/StyleSheetList.cpp

Index: Source/core/css/StyleSheetList.cpp
diff --git a/Source/core/css/StyleSheetList.cpp b/Source/core/css/StyleSheetList.cpp
index d6c754964d0e4fdc75208e64177a00eb532c3085..dbb27accb6fffc4a6bcf3fe8ef733d377961ecbb 100644
--- a/Source/core/css/StyleSheetList.cpp
+++ b/Source/core/css/StyleSheetList.cpp
@@ -24,6 +24,7 @@
 #include "core/HTMLNames.h"
 #include "core/dom/Document.h"
 #include "core/dom/StyleEngine.h"
+#include "core/frame/UseCounter.h"
 #include "core/html/HTMLStyleElement.h"
 #include "wtf/text/WTFString.h"
 
@@ -85,6 +86,8 @@ HTMLStyleElement* StyleSheetList::getNamedItem(const AtomicString& name) const
 
 CSSStyleSheet* StyleSheetList::anonymousNamedGetter(const AtomicString& name)
 {
+    if (document())
+        UseCounter::count(*document(), UseCounter::StyleSheetListAnonymousNamedGetter);
     HTMLStyleElement* item = getNamedItem(name);
     if (!item)
         return 0;