Update Background Fetch IDLs following spec changes

third_party/WebKit/LayoutTests/http/tests/background_fetch/resources/background-fetched-event-worker.js

 'use strict';
 
 importScripts('/resources/testharness.js');
 
 test(function() {
   assert_own_property(self, 'BackgroundFetchedEvent');
 
-  // The `tag` and `completedFetches` are required options in the
+  // The `tag` and `fetches` are required options in the
   // BackgroundFetchedEventInit. The latter must be a sequence of
-  // BackgroundFetchSettledRequest instances.
+  // BackgroundFetchSettledFetch instances.
   assert_throws(null, () => new BackgroundFetchedEvent('BackgroundFetchedEvent'));
   assert_throws(null, () => new BackgroundFetchedEvent('BackgroundFetchedEvent', {}));
   assert_throws(null, () => new BackgroundFetchedEvent('BackgroundFetchedEvent', { tag: 'foo' }));
-  assert_throws(null, () => new BackgroundFetchedEvent('BackgroundFetchedEvent', { tag: 'foo', completedFetches: 'bar' }));
+  assert_throws(null, () => new BackgroundFetchedEvent('BackgroundFetchedEvent', { tag: 'foo', fetches: 'bar' }));
 
-  const completedFetches = [
-    new BackgroundFetchSettledRequest(new Request('non-existing-image.png'), new Response()),
-    new BackgroundFetchSettledRequest(new Request('non-existing-image-2.png'), new Response())
+  const fetches = [
+    new BackgroundFetchSettledFetch(new Request('non-existing-image.png'), new Response()),
+    new BackgroundFetchSettledFetch(new Request('non-existing-image-2.png'), new Response())
   ];
 
   const event = new BackgroundFetchedEvent('BackgroundFetchedEvent', {
     tag: 'my-tag',
-    completedFetches
+    fetches
   });
 
   assert_equals(event.type, 'BackgroundFetchedEvent');
   assert_equals(event.cancelable, false);
   assert_equals(event.bubbles, false);
   assert_equals(event.tag, 'my-tag');
 
-  assert_true(Array.isArray(event.completedFetches));
-  assert_array_equals(event.completedFetches, completedFetches);
+  assert_true(Array.isArray(event.fetches));
+  assert_array_equals(event.fetches, fetches);
 
+  assert_inherits(event, 'updateUI');
   assert_inherits(event, 'waitUntil');
 
 }, 'Verifies that the BackgroundFetchedEvent can be constructed.');