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

third_party/WebKit/Source/core/streams/ReadableByteStreamReader.idl

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [
-    GarbageCollected,
     // We don't expose the interface now, because the name is not stable
     // enough. We will expose it in the future.
     NoInterfaceObject,
 ] interface ReadableByteStreamReader {
     [CallWith=ScriptState] readonly attribute Promise<void> closed;
     [CallWith=ScriptState] Promise<any> read();
 
     [CallWith=ScriptState] Promise<void> cancel(optional any reason);
     [RaisesException] void releaseLock();
 };