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

third_party/WebKit/Source/core/css/FontFace.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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 27 matching lines @@
 };
 
 // TODO(philipj): This interface should be [Exposed=Window,Worker].
 [
     ActiveScriptWrappable,
     DependentLifetime,
     // FIXME: This should be (DOMString or BinaryData), where BinaryData is typedef of (ArrayBuffer or ArrayBufferView)
     Constructor(DOMString family, (DOMString or ArrayBuffer or ArrayBufferView) source, optional FontFaceDescriptors descriptors),
     ConstructorCallWith=ExecutionContext,
     MeasureAs=FontFaceConstructor,
-    GarbageCollected,
 ] interface FontFace {
     [RaisesException=Setter, SetterCallWith=ExecutionContext] attribute DOMString family;
     [RaisesException=Setter, SetterCallWith=ExecutionContext] attribute DOMString style;
     [RaisesException=Setter, SetterCallWith=ExecutionContext] attribute DOMString weight;
     [RaisesException=Setter, SetterCallWith=ExecutionContext] attribute DOMString stretch;
     [RaisesException=Setter, SetterCallWith=ExecutionContext] attribute DOMString unicodeRange;
     [RaisesException=Setter, SetterCallWith=ExecutionContext] attribute DOMString variant;
     [RaisesException=Setter, SetterCallWith=ExecutionContext] attribute DOMString featureSettings;
 
     readonly attribute FontFaceLoadStatus status;
 
     [CallWith=ScriptState] Promise<FontFace> load();
     [CallWith=ScriptState] readonly attribute Promise<FontFace> loaded;
 };