[REQUIRED] Describe your environment

• Operating System version: mac os
• Firebase SDK version: 4.8.1
• Firebase Product: database

[REQUIRED] Describe the problem

browser show error When I try add firebase.js to chrome extension:
Can't load file /../firebase.js ... . Encoding is not UTF-8.

I try convert it to utf-8 but browser show error anyway

Steps to reproduce:

1. download firebase.js using https://www.gstatic.com/firebasejs/4.8.1/firebase.js
2. add firebase.js to chrome extension package
3. enable developer mode in chrome browser
4. load extension to chrome browser