Add use counters for lots of DOM APIs.

third_party/WebKit/Source/core/frame/WindowEventHandlers.idl

 /*
  * Copyright (c) 2013, Opera Software ASA. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 19 matching lines @@
 // https://html.spec.whatwg.org/multipage/webappapis.html#windoweventhandlers
 
 [
     ImplementedAs=DOMWindowEventHandlers,
     LegacyTreatAsPartialInterface,
     NoInterfaceObject, // Always used on target of 'implements'
 ] interface WindowEventHandlers {
     //attribute EventHandler onafterprint;
     //attribute EventHandler onbeforeprint;
     // FIXME: onbeforeunload should be an OnBeforeUnloadEventHandler.
-    attribute EventHandler onbeforeunload;
-    attribute EventHandler onhashchange;
-    attribute EventHandler onlanguagechange;
-    attribute EventHandler onmessage;
-    attribute EventHandler onoffline;
-    attribute EventHandler ononline;
-    attribute EventHandler onpagehide;
-    attribute EventHandler onpageshow;
-    attribute EventHandler onpopstate;
-    attribute EventHandler onrejectionhandled;
-    attribute EventHandler onstorage;
-    attribute EventHandler onunhandledrejection;
-    attribute EventHandler onunload;
+    [Measure] attribute EventHandler onbeforeunload;
+    [Measure] attribute EventHandler onhashchange;
+    [Measure] attribute EventHandler onlanguagechange;
+    [Measure] attribute EventHandler onmessage;
+    [Measure] attribute EventHandler onoffline;
+    [Measure] attribute EventHandler ononline;
+    [Measure] attribute EventHandler onpagehide;
+    [Measure] attribute EventHandler onpageshow;
+    [Measure] attribute EventHandler onpopstate;
+    [Measure] attribute EventHandler onrejectionhandled;
+    [Measure] attribute EventHandler onstorage;
+    [Measure] attribute EventHandler onunhandledrejection;
+    [Measure] attribute EventHandler onunload;
 };