Bug 1221761 - Probe.prototype.release() now swallows NS_ERROR_NOT_AVAILABLE. r=felipe

During shutdown, we may find ourselves attempting to release and shutdown a probe while the PerformanceStats service is already shutdown. In this case, since the probe is already shutdown, we can simply ignore the error.

--HG--
extra : transplant_source : %BBT%84%26.%AD%7B%23%1C%BC%3F%85%F9%18%A3%D8%84%EC%02%BE

toolkit/components/perfmonitoring/PerformanceStats.jsm

@@ -95,7 +95,15 @@ Probe.prototype = {
   release: function() {
     this._counter--;
     if (this._counter == 0) {
+      try {
         this._impl.isActive = false;
+      } catch (ex) {
+        if (ex && typeof ex == "object" && ex.result == Components.results.NS_ERROR_NOT_AVAILABLE) {
+          // The service has already been shutdown. Ignore further shutdown requests.
+          return;
+        }
+        throw ex;
+      }
       Process.broadcast("release", [this._name]);
     }
   },