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

third_party/WebKit/Source/core/html/ImageData.idl

 /*
  * Copyright (C) 2008, 2009 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
@@ skipping 15 matching lines @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 // https://html.spec.whatwg.org/#dom-imagedata
 
 [
     Constructor(unsigned long sw, unsigned long sh),
     Constructor(Uint8ClampedArray data, unsigned long sw, optional unsigned long sh),
     Exposed=(Window,Worker),
     RaisesException=Constructor,
-    GarbageCollected,
 ] interface ImageData {
     readonly attribute unsigned long width;
     readonly attribute unsigned long height;
     // TODO(philipj): Expose data.
     // readonly attribute Uint8ClampedArray data;
 };