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

third_party/WebKit/Source/core/dom/URLSearchParams.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.
 
 // https://url.spec.whatwg.org/#interface-urlsearchparams
 
 [
     Constructor(optional (USVString or URLSearchParams) init = ""),
-    GarbageCollected,
     Exposed=(Window,Worker)
 ] interface URLSearchParams {
     void append(USVString name, USVString value);
     [ImplementedAs=deleteAllWithName] void delete(USVString name);
     USVString? get(USVString name);
     sequence<USVString> getAll(USVString name);
     boolean has(USVString name);
     void set(USVString name, USVString value);
     
     iterable<USVString, USVString>;
     stringifier;
 };