Setting HTMLMediaElement.controller does not properly remove the 'mediagroup' content attribute

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 53 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
     [Reflect] attribute DOMString mediaGroup;
-    [CustomSetter] attribute MediaController controller;
+    [StrictTypeChecking] attribute MediaController controller;
 
     // controls
     attribute boolean controls;
     [SetterRaisesException] attribute double volume;
     attribute boolean muted;
     [Reflect=muted] attribute boolean defaultMuted;
 
     // tracks
     [RuntimeEnabled=VideoTrack] readonly attribute TextTrackList textTracks;
     [RuntimeEnabled=VideoTrack, 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;
 
     // FIXME: add DeprecateAs=PrefixedMediaGenerateKeyRequest when MediaKeys is ready.
     [RuntimeEnabled=PrefixedEncryptedMedia, RaisesException] void webkitGenerateKeyRequest([TreatNullAs=NullString, TreatUndefinedAs=NullString] DOMString keySystem, optional Uint8Array initData);
     [RuntimeEnabled=PrefixedEncryptedMedia, RaisesException] void webkitAddKey([TreatNullAs=NullString, TreatUndefinedAs=NullString] DOMString keySystem, Uint8Array key, optional Uint8Array initData, [Default=NullString] optional DOMString sessionId);
     [RuntimeEnabled=PrefixedEncryptedMedia, RaisesException] void webkitCancelKeyRequest([TreatNullAs=NullString, TreatUndefinedAs=NullString] DOMString keySystem, [Default=NullString] optional DOMString sessionId);
 
     [RuntimeEnabled=PrefixedEncryptedMedia] attribute EventHandler onwebkitkeyadded;
     [RuntimeEnabled=PrefixedEncryptedMedia] attribute EventHandler onwebkitkeyerror;
     [RuntimeEnabled=PrefixedEncryptedMedia] attribute EventHandler onwebkitkeymessage;
     [RuntimeEnabled=PrefixedEncryptedMedia] attribute EventHandler onwebkitneedkey;
 
     [RuntimeEnabled=EncryptedMedia, Conditional=ENCRYPTED_MEDIA_V2] attribute MediaKeys mediaKeys;
 };