Doorhanger still displayed after clicking the "Go back one page" button

[obotisan]

[Affected versions]:

• Firefox 62.0

• Firefox 63.0a1

• Firefox Monitor 2.1

[Affected Platforms]:

• Windows 10 x64
• Windows 7 x64
• macOS 10.13
• Ubuntu 16.04 x64

[Prerequisites]: Prefs you'll need to set in about:config:

• (boolean) extensions.fxmonitor.enabled - true
• (string) extensions.fxmonitor.breachListURL - https://haveibeenpwned.com/api/v2/breaches

[Steps to reproduce]:

1. Access in a new tab any of the sites from this list: https://docs.google.com/spreadsheets/d/1GYsLxXdCTlV5INzkpVBlpRPS3kfj-pTG7INOPSX6Up4/edit#gid=1389057478
2. Wait until the page is loaded and the doorhanger is displayed.
3. Click on the "Go back one page" button.

[Expected result]:

• The doorhanger is dismissed.

[Actual result]:

• The doorhanger is still displayed until you click on the URL bar .

[Regression]:

• I don't think this is a regression.

[Notes]:

• Please look at the attached gif.

[nhnt11]

This is a bug in PopupNotifications - it doesn't handle going back to the newtab page (which seems to be a problematic "feature").

I don't think we should fix this here. The same issue is observed if you trigger a permission prompt (from permission.site for example) and click the back button.

@johannhof what do you think?

[nhnt11]

This is being tracked in https://bugzilla.mozilla.org/show_bug.cgi?id=1478348. Closing this issue.