import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

devtools/server/service-worker-child.js

@@ -0,0 +1,32 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+let { classes: Cc, interfaces: Ci, utils: Cu } = Components;
+let swm = Cc["@mozilla.org/serviceworkers/manager;1"].
+  getService(Ci.nsIServiceWorkerManager);
+
+addMessageListener("serviceWorkerRegistration:start", message => {
+  let { data } = message;
+  let array = swm.getAllRegistrations();
+
+  // Find the service worker registration with the desired scope.
+  for (let i = 0; i < array.length; i++) {
+    let registration =
+      array.queryElementAt(i, Ci.nsIServiceWorkerRegistrationInfo);
+    // XXX: In some rare cases, `registration.activeWorker` can be null for a
+    // brief moment (e.g. while the service worker is first installing, or if
+    // there was an unhandled exception during install that will cause the
+    // registration to be removed). We can't do much about it here, simply
+    // ignore these cases.
+    if (registration.scope === data.scope && registration.activeWorker) {
+      // Briefly attaching a debugger to the active service worker will cause
+      // it to start running.
+      registration.activeWorker.attachDebugger();
+      registration.activeWorker.detachDebugger();
+      return;
+    }
+  }
+});