Add UseCounters for init*Event methods that aren't already measured

Source/core/events/UIEvent.idl

Index: Source/core/events/UIEvent.idl
diff --git a/Source/core/events/UIEvent.idl b/Source/core/events/UIEvent.idl
index 50e34acd34a34bf0ae0cd0f6f2ccfee7e86387d1..7cb51a83bc6b87dd553eb9564e3f1fc384c7ce32 100644
--- a/Source/core/events/UIEvent.idl
+++ b/Source/core/events/UIEvent.idl
@@ -28,11 +28,11 @@
 
     // https://w3c.github.io/uievents/#idl-interface-UIEvent-initializers
     // TODO(philipj): None of the initUIEvent() arguments should be optional.
-    void initUIEvent([Default=Undefined] optional DOMString type,
-                                    [Default=Undefined] optional boolean bubbles,
-                                    [Default=Undefined] optional boolean cancelable,
-                                    [Default=Undefined] optional Window? view,
-                                    [Default=Undefined] optional long detail);
+    [Measure] void initUIEvent([Default=Undefined] optional DOMString type,
+                               [Default=Undefined] optional boolean bubbles,
+                               [Default=Undefined] optional boolean cancelable,
+                               [Default=Undefined] optional Window? view,
+                               [Default=Undefined] optional long detail);
 
     // FIXME: these belong on the KeyboardEvent interface
     [MeasureAs=UIEventCharCode] readonly attribute long charCode;