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

third_party/WebKit/Source/core/html/track/vtt/VTTRegion.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:
  * 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 10 matching lines @@
  * 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://dev.w3.org/html5/webvtt/#the-vttregion-interface
 
 [
     Constructor,
     RuntimeEnabled=WebVTTRegions,
-    GarbageCollected,
 ] interface VTTRegion {
     [RaisesException=Setter] attribute double width;
     // TODO(philipj): height should be called lines.
     [RaisesException=Setter] attribute long height;
     [RaisesException=Setter] attribute double regionAnchorX;
     [RaisesException=Setter] attribute double regionAnchorY;
     [RaisesException=Setter] attribute double viewportAnchorX;
     [RaisesException=Setter] attribute double viewportAnchorY;
     // TODO(philip): scroll should be of type ScrollSetting.
     [RaisesException=Setter] attribute DOMString scroll;
 
     // TODO(philipj): The track/id attributes are gone from the spec:
     // https://www.w3.org/Bugs/Public/show_bug.cgi?id=24380
     readonly attribute TextTrack track;
     attribute DOMString id;
 };