Bug 1741978 - Clean up at shutdown after `--start-debugger-server`. r=devtools-reviewers,jdescottes

Differential Revision: https://phabricator.services.mozilla.com/D139152

devtools/startup/DevToolsStartup.jsm

@@ -1145,6 +1145,20 @@ DevToolsStartup.prototype = {
       const listener = new SocketListener(devToolsServer, socketOptions);
       listener.open();
       dump("Started devtools server on " + portOrPath + "\n");
+
+      // Prevent leaks on shutdown.
+      const close = () => {
+        Services.obs.removeObserver(close, "quit-application");
+        dump("Stopped devtools server on " + portOrPath + "\n");
+        if (listener) {
+          listener.close();
+        }
+        if (devToolsServer) {
+          devToolsServer.destroy();
+        }
+        serverLoader.destroy();
+      };
+      Services.obs.addObserver(close, "quit-application");
     } catch (e) {
       dump("Unable to start devtools server on " + portOrPath + ": " + e);
     }