Implement the events for Background Fetch

third_party/WebKit/Source/modules/background_fetch/ServiceWorkerGlobalScopeBackgroundFetch.h

+// 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.
+
+#ifndef ServiceWorkerGlobalScopeBackgroundFetch_h
+#define ServiceWorkerGlobalScopeBackgroundFetch_h
+
+#include "core/events/EventTarget.h"
+#include "wtf/Allocator.h"
+
+namespace blink {
+
+class ServiceWorkerGlobalScopeBackgroundFetch {
+  STATIC_ONLY(ServiceWorkerGlobalScopeBackgroundFetch);
+
+ public:
+  DEFINE_STATIC_ATTRIBUTE_EVENT_LISTENER(backgroundfetched);
+  DEFINE_STATIC_ATTRIBUTE_EVENT_LISTENER(backgroundfetchfail);
+  DEFINE_STATIC_ATTRIBUTE_EVENT_LISTENER(backgroundfetchabort);
+  DEFINE_STATIC_ATTRIBUTE_EVENT_LISTENER(backgroundfetchclick);
+};
+
+}  // namespace blink
+
+#endif  // ServiceWorkerGlobalScopeBackgroundFetch_h