[Background Fetch] Simplify fetch storage workflow.

In addition, MatchAll should return all records, including unprocessed
ones. To support this, the following changes were made:
- Creating a registration also stores all the requests with an empty
response in the cache.
- When an individual request is processed, the failure reason (if any)
is stored in the metadata.
- The logic of GetSettledFetchesTask was moved to
MarkRegistrationForDeletionTask. It checks the metadata rather than the
cache itself to find a failure reason (if any).
- Match/MatchAll logic was moved to a new database task
(MatchRequestsTask). A new API call was added to the cache storage to
allow querying request/response pairs. If a response is found to be
empty it will be exposed as a nullptr.

Change-Id: I631a3ef3da95117aed759a675fe591da5201eeca

background-fetch/abort.https.window.js

@@ -45,11 +45,14 @@ backgroundFetchTest(async (test, backgroundFetch) => {
 
       assert_equals(type, 'backgroundfetchabort');
 
+      assert_equals(results.length, 2);
+
+      const completedResult = results[0] || results[1];
       // The abort might have gone through before the first result was persisted.
-      if (results.length === 1) {
-        assert_true(results[0].url.includes('resources/feature-name.txt'));
-        assert_equals(results[0].status, 200);
-        assert_equals(results[0].text, expectedResultText);
+      if (completedResult) {
+        assert_true(completedResult.url.includes('resources/feature-name.txt'));
+        assert_equals(completedResult.status, 200);
+        assert_equals(completedResult.text, expectedResultText);
       }
 
       resolve();

background-fetch/fetch.https.window.js

@@ -265,16 +265,20 @@ backgroundFetchTest(async (test, backgroundFetch) => {
 
 backgroundFetchTest(async (test, backgroundFetch) => {
   const registration = await backgroundFetch.fetch(
-                         'my-id',
-                         ['https://example.com', 'http://example.com']);
+      'my-id',
+      [location.origin, location.origin.replace('https', 'http')]);
 
   const {type, eventRegistration, results} = await getMessageFromServiceWorker();
 
   assert_equals('backgroundfetchfail', type);
   assert_equals(eventRegistration.failureReason, 'fetch-error');
 
   assert_equals(results.length, 2);
-  assert_true(results[0].url.includes('https://example.com'));
-  assert_equals(results[1].url, '');
+
+  const validResponse = results[0] ? results[0] : results[1];
+  const nullResponse = !results[0] ? results[0] : results[1];
+
+  assert_true(validResponse.url.includes(location.origin));
+  assert_equals(nullResponse, null);
 
 }, 'Fetches with mixed content should fail.');

background-fetch/service_workers/sw.js

@@ -2,9 +2,8 @@
 importScripts('sw-helpers.js');
 
 async function getFetchResult(record) {
-  response = await record.responseReady;
-  if (!response)
-    return Promise.resolve(null);
+  const response = await record.responseReady.catch(() => null);
+  if (!response) return null;
 
   return {
     url: response.url,
@@ -13,7 +12,7 @@ async function getFetchResult(record) {
   };
 }
 
-function handleBackgroundFetchUpdateEvent(event) {
+function handleBackgroundFetchEvent(event) {
   event.waitUntil(
     event.registration.matchAll()
       .then(records =>
@@ -25,6 +24,6 @@ function handleBackgroundFetchUpdateEvent(event) {
       }));
 }
 
-self.addEventListener('backgroundfetchsuccess', handleBackgroundFetchUpdateEvent);
-self.addEventListener('backgroundfetchfail', handleBackgroundFetchUpdateEvent);
-self.addEventListener('backgroundfetchabort', handleBackgroundFetchUpdateEvent);
+self.addEventListener('backgroundfetchsuccess', handleBackgroundFetchEvent);
+self.addEventListener('backgroundfetchfail', handleBackgroundFetchEvent);
+self.addEventListener('backgroundfetchabort', handleBackgroundFetchEvent);