Background Fetch: use permission context directly when initiating fetch.

This reduces duplicated logic between BackgroundFetchDelegateImpl and
BackgroundFetchPermissionContext. It also forces the logic to align.
Specifically, the permission context returned ALLOW when automatic DLs
were allowed, but the implementation enforced ASK even if auto DLs
are allowed.

This temporarily regresses WebLayer because there's no
Background Fetch permission context there, but that will be addressed
soon.

Bug: 1189247, 1057770
Change-Id: I5441f00835c186826927d2ef38612c8e55eb049f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2800512
Commit-Queue: Evan Stade <[email protected]>
Reviewed-by: Nasko Oskov <[email protected]>
Reviewed-by: Mugdha Lakhani <[email protected]>
Cr-Commit-Position: refs/heads/master@{#872641}

background-fetch/resources/utils.js

@@ -2,6 +2,15 @@
 
 let nextBackgroundFetchId = 0;
 
+function loadScript(path) {
+  let script = document.createElement('script');
+  let promise = new Promise(resolve => script.onload = resolve);
+  script.src = path;
+  script.async = false;
+  document.head.appendChild(script);
+  return promise;
+}
+
 // Waits for a single message received from a registered Service Worker.
 async function getMessageFromServiceWorker() {
   return new Promise(resolve => {
@@ -39,6 +48,13 @@ async function registerAndActivateServiceWorker(test, name) {
 // directory to register.
 function backgroundFetchTest(func, description, workerName = 'sw.js') {
   promise_test(async t => {
+    if (typeof test_driver === 'undefined') {
+      await loadScript('/resources/testdriver.js');
+      await loadScript('/resources/testdriver-vendor.js');
+    }
+
+    await test_driver.set_permission({name: 'background-fetch'}, 'granted');
+
     const serviceWorkerRegistration =
         await registerAndActivateServiceWorker(t, workerName);
     serviceWorkerRegistration.active.postMessage(null);