Add UseCounters for UIEvent.charCode/keyCode/which

Source/core/events/KeyboardEvent.idl

Index: Source/core/events/KeyboardEvent.idl
diff --git a/Source/core/events/KeyboardEvent.idl b/Source/core/events/KeyboardEvent.idl
index ca68d367b11da44762ffd95436da0110eaed41f0..f789f02249d90366cd235ef6c7d29d5f2766061c 100644
--- a/Source/core/events/KeyboardEvent.idl
+++ b/Source/core/events/KeyboardEvent.idl
@@ -48,5 +48,8 @@
                            [Default=Undefined] optional boolean altKey,
                            [Default=Undefined] optional boolean shiftKey,
                            [Default=Undefined] optional boolean metaKey);
-};
 
+    readonly attribute long charCode;
+    readonly attribute long keyCode;
+    readonly attribute long which;
+};