Bug 1513855: Make sure that quit-application-granted and quit-application notifications are always sent. r=froydnj

We only run the main event loop if at least one window is open. There are various
cases where this doesn't happen, such as -silent. By the time we get there though
some components have started and require appropriate notifications to tell them
to shutdown safely. This patch sends the quit-application-granted and
quit-application notifications in the case that there were no windows open
and nsAppStartup::Quit hasn't already been called when we come to run the
event loop.

Differential Revision: https://phabricator.services.mozilla.com/D51736

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extra : moz-landing-system : lando