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

third_party/WebKit/Source/modules/bluetooth/BluetoothRemoteGATTCharacteristic.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://webbluetoothchrome.github.io/web-bluetooth/#idl-def-bluetoothgattcharacteristic
 
 // Implement BluetoothRemoteGATTCharacteristic interface: https://crbug.com/483344
 
 [
-    GarbageCollected,
     DependentLifetime,
     OriginTrialEnabled=WebBluetooth,
 ] interface BluetoothRemoteGATTCharacteristic : EventTarget {//: CharacteristicEventHandlers {
     // TODO(ortuno): Add test to make sure service matches the service
     // used to call getCharacteristic.
     // readonly    attribute BluetoothRemoteGATTService     service;
     readonly    attribute UUID                  uuid;
     readonly    attribute BluetoothCharacteristicProperties properties;
     readonly    attribute DataView?             value;
     // Promise<BluetoothRemoteGATTDescriptor>           getDescriptor(BluetoothDescriptorUUID descriptor);
     // Promise<sequence<BluetoothRemoteGATTDescriptor>> getDescriptors(optional BluetoothDescriptorUUID descriptor);
     [CallWith=ScriptState] Promise<DataView>    readValue();
     [CallWith=ScriptState] Promise<void>        writeValue(BufferSource value);
     [CallWith=ScriptState] Promise<void>        startNotifications();
     [CallWith=ScriptState] Promise<void>        stopNotifications();
 
     // TODO(ortuno): Move this to CharacteristicEventHandlers.
     // http://crbug.com/537459
     attribute EventHandler oncharacteristicvaluechanged;
 };