Implement the events for Background Fetch

third_party/WebKit/Source/modules/background_fetch/BackgroundFetchFailEvent.idl

Index: third_party/WebKit/Source/modules/background_fetch/BackgroundFetchFailEvent.idl
diff --git a/third_party/WebKit/Source/modules/background_fetch/BackgroundFetchFailEvent.idl b/third_party/WebKit/Source/modules/background_fetch/BackgroundFetchFailEvent.idl
new file mode 100644
index 0000000000000000000000000000000000000000..d1881e421e8754d2ac034aea2e0fcdbf859f76d9
--- /dev/null
+++ b/third_party/WebKit/Source/modules/background_fetch/BackgroundFetchFailEvent.idl
@@ -0,0 +1,13 @@
+// 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.
+
+// https://wicg.github.io/background-fetch/#background-fetch-fail-event
+
+[
+    Constructor(DOMString type, BackgroundFetchFailEventInit init),
+    Exposed=ServiceWorker,
+    RuntimeEnabled=BackgroundFetch
+] interface BackgroundFetchFailEvent : BackgroundFetchEvent {
+    // TODO(peter): Implement the `failedFetches` attribute.
+};