Hook up the other Background Fetch Mojo methods with the system

third_party/WebKit/LayoutTests/http/tests/background_fetch/background-fetch-manager-getTags.https.html

Index: third_party/WebKit/LayoutTests/http/tests/background_fetch/background-fetch-manager-getTags.https.html
diff --git a/third_party/WebKit/LayoutTests/http/tests/background_fetch/background-fetch-manager-getTags.https.html b/third_party/WebKit/LayoutTests/http/tests/background_fetch/background-fetch-manager-getTags.https.html
index bee0cc8833dc117eabcfe68ef34ef855569968f7..381d68dc57ccc9c8e7275e4089fa735d619d9003 100644
--- a/third_party/WebKit/LayoutTests/http/tests/background_fetch/background-fetch-manager-getTags.https.html
+++ b/third_party/WebKit/LayoutTests/http/tests/background_fetch/background-fetch-manager-getTags.https.html
@@ -43,4 +43,26 @@ promise_test(function(test) {
     });
 
 }, 'BackgroundFetchManager.getTags() returns an empty sequence by default.');
+
+promise_test(function(test) {
+  const tags = ['first-tag', 'second-tag', 'third-tag'];
+
+  let registration = null;
+
+  return service_worker_unregister_and_register(test, workerUrl, scope)
+    .then(r => {
+      registration = r;
+      return wait_for_state(test, r.installing, 'activated');
+    })
+    .then(() => {
+      return Promise.all(
+        tags.map(tag => registration.backgroundFetch.fetch(tag, ['resources/non-existing-file.png'])));
+    })
+    .then(() => registration.backgroundFetch.getTags())
+    .then(receivedTags => {
+      assert_array_equals(receivedTags, tags);
+    });
+
+}, 'BackgroundFetchManager.getTags() returns a sequence of active fetches.');
+
 </script>