Make 'crossOrigin' IDL attributes nullable

Source/core/html/HTMLMediaElement.idl

 /*
  * Copyright (C) 2007, 2010, 2011, 2012 Apple 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:
  * 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 18 matching lines @@
     SpecialWrapFor=(HTMLAudioElement,HTMLVideoElement),
     TypeChecking=Unrestricted,
 ] interface HTMLMediaElement : HTMLElement {
 
     // error state
     readonly attribute MediaError? error;
 
     // network state
     [Reflect, URL] attribute DOMString src;
     [URL] readonly attribute DOMString currentSrc;
-    [Reflect, ReflectOnly=("anonymous","use-credentials"), ReflectEmpty="anonymous", ReflectInvalid="anonymous"] attribute DOMString crossOrigin;
+    [Reflect, ReflectOnly=("anonymous","use-credentials"), ReflectEmpty="anonymous", ReflectInvalid="anonymous"] attribute DOMString? crossOrigin;
 
     const unsigned short NETWORK_EMPTY = 0;
     const unsigned short NETWORK_IDLE = 1;
     const unsigned short NETWORK_LOADING = 2;
     const unsigned short NETWORK_NO_SOURCE = 3;
     readonly attribute unsigned short networkState;
     attribute DOMString preload;
 
     readonly attribute TimeRanges buffered;
     void load();
@@ skipping 39 matching lines @@
     [RaisesException] TextTrack addTextTrack(DOMString kind, optional DOMString label, optional DOMString language);
 
     // WebKit extensions
 
     // The number of bytes consumed by the media decoder.
     [MeasureAs=PrefixedAudioDecodedByteCount] readonly attribute unsigned long webkitAudioDecodedByteCount;
     [MeasureAs=PrefixedVideoDecodedByteCount] readonly attribute unsigned long webkitVideoDecodedByteCount;
 
     [Reflect, RuntimeEnabled=SubresourceIntegrity] attribute DOMString integrity;
 };