Bug 1686816 - ensure we have useful values for waitCount and deselectCount to avoid 'undefined' showing up in telemetry, r=jaws

Unfortunately a meaningful automated test here is difficult because we're dealing with shutdown.

Differential Revision: https://phabricator.services.mozilla.com/D102598

browser/modules/ProcessHangMonitor.jsm

@@ -664,6 +664,8 @@ var ProcessHangMonitor = {
     if (this._shuttingDown) {
       this.stopHang(report, "shutdown-in-progress", {
         lastReportFromChild: now,
+        waitCount: 0,
+        deselectCount: 0,
       });
       return;
     }