Web Animations: Throw exceptions for play/pause/reverse/finish with infinite end time

third_party/WebKit/Source/core/animation/Animation.idl

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 25 matching lines @@
     ActiveDOMObject,
     NoInterfaceObject,
 ] interface Animation : EventTarget {
     // TODO(dstockwell): Add timeline property.
     [RuntimeEnabled=WebAnimationsAPI] attribute AnimationEffectReadOnly? effect;
     [Measure] attribute double?    startTime;
     [Measure] attribute double?    currentTime;
     [Measure] attribute double     playbackRate;
     [Measure] readonly attribute AnimationPlayState playState;
     [Measure, RaisesException] void finish();
-    [Measure] void play();
-    [Measure] void pause();
-    [Measure] void reverse();
+    [Measure, RaisesException] void play();
+    [Measure, RaisesException] void pause();
+    [Measure, RaisesException] void reverse();
     [Measure] attribute DOMString id;
-
     [Measure] void cancel();
     [Measure] attribute EventHandler onfinish;
     [Measure] attribute EventHandler oncancel;
     [RuntimeEnabled=WebAnimationsAPI, CallWith=ScriptState] readonly attribute Promise<Animation> finished;
     [RuntimeEnabled=WebAnimationsAPI, CallWith=ScriptState] readonly attribute Promise<Animation> ready;
 };