Implement WindowTimers.set{Timeout,Interval} without [Custom]

Source/core/frame/WindowTimers.idl

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Google Inc. All rights reserved.
  * Copyright (C) 2013 Samsung Electronics. 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.
@@ skipping 14 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 // http://www.whatwg.org/specs/web-apps/current-work/multipage/timers.html#windowtimers
 
 [
     ImplementedAs=DOMWindowTimers,
     LegacyTreatAsPartialInterface,
     NoInterfaceObject, // Always used on target of 'implements'
 ] interface WindowTimers {
-    // FIXME: currently using [Custom] and |any| because overload algorithm
-    // can't handle Function/DOMString overload properly
-    // http://crbug.com/293561
     // FIXME: would be clearer as a union type, like:
     // typedef (Function or DOMString) Handler
     // Needs spec update and better union support: http://crbug.com/240176
-    [Custom] long setTimeout(any handler, [Default=Undefined] optional long timeout);
-    void clearTimeout([Default=Undefined] optional long handle);
-    [Custom] long setInterval(any handler, [Default=Undefined] optional long timeout);
-    void clearInterval([Default=Undefined] optional long handle);
+    [CallWith=ScriptState] long setTimeout(Function handler, optional long timeout = 0, any... arguments);
+    [CallWith=ScriptState] long setTimeout(DOMString handler, optional long timeout = 0, any... arguments);
+    void clearTimeout(optional long handle = 0);
+    [CallWith=ScriptState] long setInterval(Function handler, optional long timeout = 0, any... arguments);
+    [CallWith=ScriptState] long setInterval(DOMString handler, optional long timeout = 0, any... arguments);
+    void clearInterval(optional long handle = 0);
 };