Add TypeChecking=Unrestricted to Web Animation APIs

Source/core/animation/Timing.idl

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [
+    ImplementedAs=AnimationNodeTiming,
     RuntimeEnabled=WebAnimationsAPI,
-    ImplementedAs=AnimationNodeTiming,
+    TypeChecking=Unrestricted,
     WillBeGarbageCollected,
 ] interface Timing {
     attribute double delay;
     attribute double endDelay;
     attribute DOMString fill;
     attribute double iterationStart;
-    attribute double iterations;
-    attribute (double or DOMString) duration;
+    attribute unrestricted double iterations;
+    attribute (unrestricted double or DOMString) duration;
     attribute double playbackRate;
     attribute DOMString direction;
     attribute DOMString easing;
 };