Service Worker: respondWith() invokes stopImmediatePropagation()

LayoutTests/http/tests/serviceworker/resources/fetch-event-respond-with-stops-propagation-worker.js

+var result = null;
+
+self.addEventListener('message', function(event) {
+    event.data.port.postMessage(result);
+  });
+
+self.addEventListener('fetch', function(event) {
+    if (!result)
+      result = 'PASS';
+    event.respondWith(new Response());
+  });
+
+self.addEventListener('fetch', function(event) {
+    result = 'FAIL: fetch event propagated';
+  });