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

third_party/WebKit/Source/modules/bluetooth/BluetoothDevice.idl

 // Copyright 2014 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://webbluetoothchrome.github.io/web-bluetooth/#idl-def-bluetoothdevice
 
 // Implement BluetoothDevice interface: http://crbug.com/421668
 
 enum VendorIDSource {
     "bluetooth",
     "usb"
 };
 
 [
-    GarbageCollected,
     DependentLifetime,
     OriginTrialEnabled=WebBluetooth,
 ] interface BluetoothDevice : EventTarget
 // Implement ServiceEventHandlers interface: http://crbug.com/421670
 // : ServiceEventHandlers
 {
 // Implement BluetoothDevice interface: http://crbug.com/421668
     [DeprecateAs=BluetoothDeviceInstanceId, ImplementedAs=id] readonly attribute DOMString instanceID;
     readonly    attribute DOMString id;
     readonly    attribute DOMString?                 name;
     readonly    attribute BluetoothAdvertisingData   adData;
     readonly    attribute unsigned long?             deviceClass;
     readonly    attribute VendorIDSource?            vendorIDSource;
     readonly    attribute unsigned long?             vendorID;
     readonly    attribute unsigned long?             productID;
     readonly    attribute unsigned long?             productVersion;
     readonly    attribute BluetoothRemoteGATTServer  gatt;
     readonly    attribute UUID[]                     uuids;
     [CallWith=ScriptState, DeprecateAs=BluetoothDeviceConnectGATT] Promise<BluetoothRemoteGATTServer> connectGATT ();
 
     attribute EventHandler ongattserverdisconnected;
 };