Bug 888058 - SimplePush: catch ping exception. r=dougt

dom/push/src/PushService.jsm

@@ -678,8 +678,15 @@ this.PushService = {
     else if (this._currentState == STATE_READY) {
       // Send a ping.
       // Bypass the queue; we don't want this to be kept pending.
-      this._ws.sendMsg('{}');
-      debug("Sent ping.");
+      // Watch out for exception in case the socket has disconnected.
+      // When this happens, we pretend the ping was sent and don't specially
+      // handle the exception, as the lack of a pong will lead to the socket
+      // being reset.
+      try {
+        this._ws.sendMsg('{}');
+      } catch (e) {
+      }
+
       this._waitingForPong = true;
       this._setAlarm(prefs.get("requestTimeout"));
     }