This is coming from FF. Here is some source...
Line 13 is this: let Ci = Components;
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at
mozilla.org/MPL/2.0/
. */
"use strict";
/* Trick the linker in order to avoid error on `Components.interfaces` usage.
We are tricking the linker with `require('./content-proxy.js')` from
worjer.js in order to ensure shipping this file! But then the linker think
that this file is going to be used as a CommonJS module where we forbid usage
of `Components`.
*/
let Ci = Components;
/**
* Access key that allows privileged code to unwrap proxy wrappers through
* valueOf:
* let xpcWrapper = proxyWrapper.valueOf(UNWRAP_ACCESS_KEY);
* This key should only be used by proxy unit test.
*/
const UNWRAP_ACCESS_KEY = {};