[BackgroundFetch] Part 2: Implement BackgroundFetchFailureReason.

This is the second part, the plumbing on the blink side.

Bug: 876691, 869918
Change-Id: I62fe4aaf37f41b5ebd341ce4731f7fda1d486feb
Reviewed-on: https://chromium-review.googlesource.com/1185015
Commit-Queue: Mugdha Lakhani <nator@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585906}

background-fetch/fetch.https.window.js

@@ -73,12 +73,18 @@ backgroundFetchTest(async (test, backgroundFetch) => {
   assert_equals(registration.uploadTotal, 0);
   assert_equals(registration.uploaded, 0);
   assert_equals(registration.downloadTotal, 0);
+  assert_equals(registration.state, "pending");
+  assert_equals(registration.failureReason, "");
   // Skip `downloaded`, as the transfer may have started already.
 
-  const {type, results} = await getMessageFromServiceWorker();
+  const {type, eventRegistration, results} = await getMessageFromServiceWorker();
   assert_equals('backgroundfetchsuccess', type);
   assert_equals(results.length, 1);
 
+  assert_equals(eventRegistration.id, registration.id);
+  assert_equals(eventRegistration.state, "success");
+  assert_equals(eventRegistration.failureReason, "");
+
   assert_true(results[0].url.includes('resources/feature-name.txt'));
   assert_equals(results[0].status, 200);
   assert_equals(results[0].text, 'Background Fetch');

background-fetch/get.https.window.js

@@ -41,6 +41,8 @@ backgroundFetchTest(async (test, backgroundFetch) => {
   assert_equals(registration.uploadTotal, 0);
   assert_equals(registration.uploaded, 0);
   assert_equals(registration.downloadTotal, 1234);
+  assert_equals(registration.state, "pending");
+  assert_equals(registration.failureReason, "");
   // Skip `downloaded`, as the transfer may have started already.
 
   const secondRegistration = await backgroundFetch.get(registrationId);

background-fetch/service_workers/sw-helpers.js

@@ -5,6 +5,25 @@ function sendMessageToDocument(msg) {
   source.postMessage(msg);
 }
 
+// This is needed to create a local javascript object identical to the
+// one returned by a BackgroundFetchEvent, so that it can be serialized
+// and transmitted from the service worker context to the document.
+function cloneRegistration(registration) {
+  function deepCopy(src) {
+    if (typeof src !== 'object' || src === null)
+        return src;
+    var dst = Array.isArray(src) ? [] : {};
+    for (var property in src) {
+        if (typeof src[property] === 'function')
+            continue;
+        dst[property] = deepCopy(src[property]);
+    }
+    return dst;
+  }
+
+  return deepCopy(registration);
+}
+
 // Notify the document that the SW is registered and ready.
 self.addEventListener('message', event => {
   source = event.source;

background-fetch/service_workers/sw.js

@@ -17,5 +17,8 @@ self.addEventListener('backgroundfetchsuccess', event => {
   event.waitUntil(
     event.registration.matchAll()
       .then(records => Promise.all(records.map(record => getFetchResult(record))))
-      .then(results => sendMessageToDocument({ type: event.type, results })));
+      .then(results => {
+        const registrationCopy = cloneRegistration(event.registration);
+        sendMessageToDocument({ type: event.type, eventRegistration: registrationCopy, results })
+      }));
 });