1473904 - The new/blank tab is not being restored when reopening the browser (set to restore the previous session)

Status: NEW

(Firefox :: Session Restore, defect, P4)

Description

[Daniel Bodea [:danibodea]]

[Affected versions]:
- Nightly v63.0a1
- Beta v62.0b5
- Release v61.0.1

[Affected platforms]:
- Windows 10, Ubuntu 16.04, Mac OS X 10.12.6

[Steps to reproduce]:
1. Open Firefox with a new profile
2. Set from Menu -> Preferences -> "Restore previous session"
3. Open a blank tab and close all other tabs
4. Open a new window and set a homepage, for example, www.google.com
5. Close the window from step 4
6. Close the window from step 3
7. Reopen the Firefox using the same profile from step 1. 

[Expected result]:
- The blank tab is opened upon reopening the browser (set to restore the previous session by default); This is because the blank tab was the last tab/windows being closed.

[Actual result]:
- The page opened in step 4 (closed in step 5) is being opened upon reopening the browser.

[Note]:
While attempting to analyse whether this is a regression or not, I tested every every decimal build until the version 20.0, where the reproduction of the issue is different:
Upon reopening the version 20 browser, both the windows closed are being reopened.