Bug 1825740 - Make PushServiceWebSocket cancel the request timeout timer when receiving a pong, r=lina.

Differential Revision: https://phabricator.services.mozilla.com/D174234

dom/push/PushServiceWebSocket.sys.mjs

@@ -1163,6 +1163,9 @@ export var PushServiceWebSocket = {
 
     // If it is a ping, do not handle the message.
     if (doNotHandle) {
+      if (!this._hasPendingRequests()) {
+        this._requestTimeoutTimer.cancel();
+      }
       return;
     }