Drop [TypeChecking=Nullable]; deduce from attribute type instead

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 12 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 [
     ActiveDOMObject,
     RuntimeEnabled=Media,
     TypeChecking=Unrestricted,
 ] interface HTMLMediaElement : HTMLElement {
 
     // error state
-    [TypeChecking=Interface|Nullable] readonly attribute MediaError? error;
+    readonly attribute MediaError? error;
 
     // network state
     [Reflect, URL, LogActivity=SetterOnly] attribute DOMString src;
     [URL, LogActivity=SetterOnly] readonly attribute DOMString currentSrc;
     [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;
@@ skipping 22 matching lines @@
     readonly attribute TimeRanges played;
     readonly attribute TimeRanges seekable;
     readonly attribute boolean ended;
     [Reflect] attribute boolean autoplay;
     [Reflect] attribute boolean loop;
     void play();
     void pause();
 
     // media controller
     [RuntimeEnabled=MediaController, Reflect] attribute DOMString mediaGroup;
-    [RuntimeEnabled=MediaController, TypeChecking=Interface|Nullable] attribute MediaController? controller;
+    [RuntimeEnabled=MediaController, TypeChecking=Interface] attribute MediaController? controller;
 
     // controls
     attribute boolean controls;
     [RaisesException=Setter] attribute double volume;
     attribute boolean muted;
     [Reflect=muted] attribute boolean defaultMuted;
 
     // tracks
     [RuntimeEnabled=AudioVideoTracks] readonly attribute AudioTrackList audioTracks;
     [RuntimeEnabled=AudioVideoTracks] readonly attribute VideoTrackList videoTracks;
     readonly attribute TextTrackList textTracks;
     [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;
 };