Have bindings layer assume and insist that all interface types are GCed.

third_party/WebKit/Source/modules/mediastream/MediaStream.idl

 /*
  * Copyright (C) 2011 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:
  * 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
  *     documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
  * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 // http://w3c.github.io/mediacapture-main/getusermedia.html#idl-def-MediaStream
 
 [
-    GarbageCollected,
     Constructor,
     Constructor(MediaStream stream),
     Constructor(MediaStreamTrack[] tracks),
     ConstructorCallWith=ExecutionContext,
     NoInterfaceObject,
 ] interface MediaStream : EventTarget {
 
     readonly attribute DOMString id;
 
     sequence<MediaStreamTrack> getAudioTracks();
     sequence<MediaStreamTrack> getVideoTracks();
     sequence<MediaStreamTrack> getTracks();
 
     [RaisesException] void addTrack(MediaStreamTrack track);
     [RaisesException] void removeTrack(MediaStreamTrack track);
     MediaStreamTrack getTrackById(DOMString trackId);
     [CallWith=ExecutionContext] MediaStream clone();
 
     readonly attribute boolean active;
 
     attribute EventHandler onactive;
     attribute EventHandler oninactive;
     //  DEPRECATED
     [MeasureAs=MediaStreamOnEnded] attribute EventHandler onended;
 
     attribute EventHandler onaddtrack;
     attribute EventHandler onremovetrack;
 };