SignInWithRedirect with Google provider does not work inside content script in chrome extension in v4.1.2

Browser: Chrome and Firefox
Browser version: Firefox v52 and Chrome v58
Operating system: MaxOS
Operating system version: v10.12.5

**What steps will reproduce the problem:**

1. git clone https://github.com/sachinjain024/practicebook practicebook
2. Go to chrome://settings
3. Enable Developer Mode
4. Click on Load unpacked extension
5. Select the directory web-extensions-master/firebase-authentication
6. Open http://www.requestly.in
7. Click on Login with Firebase
8. After login, click on 'Login Status`
9. It says - No user is logged in

**What is the expected result?**
User should be logged in. Similar behaviour works well in Firebase v1 but faced this issue when trying to upgrade to v4.

**What happens instead of that?**
User is taken to google signin screen and then he comes back to original site. Now when we check for current login status of user, it says user is not logged in.

**Please provide any other information below, and attach a screenshot if possible.**
I have asked similar question here: https://stackoverflow.com/questions/44858133/using-authentication-inside-firebase-as-content-script-in-chrome-extension

**Screenshots**