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

third_party/WebKit/Source/core/fileapi/FileReader.idl

 /*
  * Copyright (C) 2010 Google Inc.  All rights reserved.
  * Copyright (C) 2011 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 15 matching lines @@
  * 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.
  */
 
 // https://w3c.github.io/FileAPI/#APIASynch
 
 [
     ActiveScriptWrappable,
-    GarbageCollected,
     DependentLifetime,
     Constructor,
     ConstructorCallWith=ExecutionContext,
     Exposed=(Window,Worker),
 ] interface FileReader : EventTarget {
     // async read methods
     [RaisesException] void readAsArrayBuffer(Blob blob);
     // TODO(philipj): readAsBinaryString() was removed from the spec in 2012:
     // https://github.com/w3c/FileAPI/commit/8cce54559dc27bf8b8244f3f0ca9fb3e4d96efdb
     [RaisesException, Measure] void readAsBinaryString(Blob blob);
@@ skipping 16 matching lines @@
     [Measure] readonly attribute FileError? error;
 
     // event handler attributes
     attribute EventHandler onloadstart;
     attribute EventHandler onprogress;
     attribute EventHandler onload;
     attribute EventHandler onabort;
     attribute EventHandler onerror;
     attribute EventHandler onloadend;
 };