Bug 1513855 ensure we notify quit application when running silent r=kmag

Running with -silent does not result in the quit application granted notification.
Without that notification, we have a deadlock in EnvironmentAddonBuilder where it blocks
beforeShutdown waiting on the XPIDatabase to load.

Differential Revision: https://phabricator.services.mozilla.com/D41877

--HG--
extra : moz-landing-system : lando

browser/components/BrowserContentHandler.jsm

@@ -1034,6 +1034,11 @@ nsDefaultCommandLineHandler.prototype = {
       if (win) {
         win.close();
       }
+      // If this is a silent run, we must notify shutdown so that the
+      // quit-application-granted notification will happen.  This is
+      // required in the AddonManager to properly handle shutdown
+      // blockers for Telemetry and XPIDatabase.
+      Services.startup.quit(Services.startup.eForceQuit);
     }
   },