getMostRecentBrowserWindow uses win.document.documentElement.getAttribute("chromehidden"). The read-only location bar, the disabled history button and the hidden tabstrip depend on !win.toolbar.visible.
So in window with a chromehidden attribute that's non-empty and doesn't contain "toolbar", external links won't open, but the user can type new addresses, open new tabs, etc..
Dão, can you provide some STR here? I'm trying to figure out what this bug is about and whether it's still valid.
See the URL field. You may also want to look at the getMostRecentBrowserWindow implementation and look for toolbar.visible in browser.js.
Created attachment 590170 [details] [diff] [review]