Add use counters for "IE Extensions" to the Event interface

Source/core/events/Event.idl

Index: Source/core/events/Event.idl
diff --git a/Source/core/events/Event.idl b/Source/core/events/Event.idl
index 59b39a413db8d0e08f35074cc7705ac2d21ae6b0..4a803dda61d6bfbdeac90c25c696e05cfa3edf05 100644
--- a/Source/core/events/Event.idl
+++ b/Source/core/events/Event.idl
@@ -68,11 +68,9 @@
     void stopImmediatePropagation();
 
     // IE Extensions
-    readonly attribute EventTarget      srcElement;
+    [MeasureAs=EventSrcElement] readonly attribute EventTarget srcElement;
     [ImplementedAs=legacyReturnValue, MeasureAs=EventReturnValue] attribute boolean returnValue;
-             attribute boolean          cancelBubble;
-
-    readonly attribute NodeList path;
-
-    [Custom=Getter] readonly attribute DataTransfer clipboardData;
+    [MeasureAs=EventCancelBubble] attribute boolean cancelBubble;
+    [MeasureAs=EventPath] readonly attribute NodeList path;
+    [Custom=Getter, MeasureAs=EventClipboardData] readonly attribute DataTransfer clipboardData;
 };