Fix prevent session loss when library is closed after main window (#11073)

[Radless0]

Closing the Library window after the main window used to clear the session state completely; this patch ensures session save is skipped for non-browser windows and adds a test to cover this scenario.

Fix: #11073

[mr-cheffy]

Would it also be interesting to also ignore private windows?

[Radless0]

Would it also be interesting to also ignore private windows?

As far as I know, private windows are already excluded from session restore by design, so I think it’s unnecessary to handle them here as well.

[mr-cheffy]

I dont understand the patch then, because this check for "navigator:browser", isn't it done before by checking if __Ssi exists on the window's attributes?

[Radless0]

I dont understand the patch then, because this check for "navigator:browser", isn't it done before by checking if __Ssi exists on the window's attributes?

In Zen, private windows are handled as a completely separate process (Zen Private Browsing), so they don’t interact with the main session store at all, that’s why I didn’t include them in this patch.

As for the navigator:browser check in Zen, secondary windows like the Library still run inside the main process and may still expose session-related attributes such as __Ssi. That’s why the extra navigator:browser check is needed: it ensures only real browser windows affect the session state when closing.

[mr-cheffy]

Wouldn't it be more interesting to submit this patch to upstream firefox?