Measure how often Attr needs its associated Element

Source/core/dom/Attr.idl

Index: Source/core/dom/Attr.idl
diff --git a/Source/core/dom/Attr.idl b/Source/core/dom/Attr.idl
index a2fab303c4f729f7f69e68fa415402344a7a67c8..2a2e13419177d452eaf7c10fa777013b7268914c 100644
--- a/Source/core/dom/Attr.idl
+++ b/Source/core/dom/Attr.idl
@@ -26,12 +26,14 @@ interface Attr : Node {
 
     [MeasureAs=AttributeSpecified] readonly attribute boolean specified;
 
-    [TreatReturnedNullStringAs=Null, TreatNullAs=NullString, RaisesException=Setter, CustomElementCallbacks] attribute DOMString value;
+    [ImplementedAs=valueForBindings, TreatReturnedNullStringAs=Null, TreatNullAs=NullString, CustomElementCallbacks] attribute DOMString value;
 
     // DOM 4
 
     [TreatReturnedNullStringAs=Null, PerWorldBindings] readonly attribute DOMString prefix;
     [TreatReturnedNullStringAs=Null, PerWorldBindings] readonly attribute DOMString namespaceURI;
     [TreatReturnedNullStringAs=Null, PerWorldBindings] readonly attribute DOMString localName;
-};
 
+    // Node override to measure usage.
+    [MeasureAs=AttrNodeValue, TreatReturnedNullStringAs=Null, TreatNullAs=NullString, CustomElementCallbacks] attribute DOMString nodeValue;
+};