Add a UseCounter for Element.webkitMatchesSelector

Source/core/dom/Element.idl

Index: Source/core/dom/Element.idl
diff --git a/Source/core/dom/Element.idl b/Source/core/dom/Element.idl
index 3d1a43f776d8d590013b412cd955cd8931d22184..eb55c2e7090ca9f7caa8ef0079ec9c395c95f56b 100644
--- a/Source/core/dom/Element.idl
+++ b/Source/core/dom/Element.idl
@@ -97,8 +97,8 @@
     [RaisesException] Element querySelector(DOMString selectors);
     [RaisesException] NodeList querySelectorAll(DOMString selectors);
 
-    // WebKit extension, pending specification.
-    [RaisesException] boolean webkitMatchesSelector([Default=Undefined] optional DOMString selectors);
+    // WebKit extension
+    [RaisesException, MeasureAs=ElementPrefixedMatchesSelector] boolean webkitMatchesSelector([Default=Undefined] optional DOMString selectors);
 
     // Shadow DOM API
     [RuntimeEnabled=ShadowDOM, Reflect, TreatNullAs=NullString, PerWorldBindings] attribute DOMString pseudo;