Implement a Mojo service for Background Fetch

third_party/WebKit/public/platform/modules/background_fetch/background_fetch.mojom

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+module blink.mojom;
+
+enum BackgroundFetchError {
+  NONE,
+  DUPLICATED_TAG
+};
+
+struct IconDefinition {
+  string src;
+  string sizes;
+  string type;
+};
+
+struct BackgroundFetchRegistration {
+  string tag;
+  array<IconDefinition> icons;
+  int64 total_download_size = 0;
+  string title = "";

[dcheng, 2017/03/16 07:14:08]

Just curious, but how does default initialization work? I would have imagined
this is the default state, but I'm not sure.

[Peter Beverloo, 2017/03/16 16:26:55]

I'm not sure, I did the copy-from-prior-art thing. At the very least it's
semantical in creating a distinguishment between required and optional w/
default value.

Looking at the generated code, it does consider what's being defined here.

+};
+
+interface BackgroundFetchService {
+  // TODO(peter): Implement support for the `fetch()` function in Mojo.
+
+  // Updates the user interface for the Background Fetch identified by the
+  // |service_worker_registration_id| and the |tag|.
+  UpdateUI(int64 service_worker_registration_id, string tag, string title)
+      => (BackgroundFetchError error);
+
+  // Aborts the Background Fetch registration identified by the
+  // |service_worker_registration_id| and the |tag|.
+  Abort(int64 service_worker_registration_id, string tag);
+
+  // Gets the Background Fetch registration identified by the
+  // |service_worker_registration_id| and the |tag|.
+  GetRegistration(int64 service_worker_registration_id, string tag)
+      => (BackgroundFetchError error,
+          BackgroundFetchRegistration? registration);
+
+  // Gets the sequence of tags for active Background Fetch registrations given
+  // the |service_worker_registration_id|.
+  GetTags(int64 service_worker_registration_id)
+      => (BackgroundFetchError error,
+          array<string> tags);
+};