Add the Blink APIs for the WebNotificationManager.

public/platform/WebNotificationDelegate.h

+// Copyright 2014 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 WebNotificationDelegate_h
+#define WebNotificationDelegate_h
+
+namespace blink {
+
+// A delegate through which the embedder can trigger events on a Document-bound
+// Web Notifications object. Service Worker-bound Web Notifications will not have
+// a delegate, as their events will be fired on a Service Worker instead.
+class WebNotificationDelegate {
+public:
+    virtual void dispatchClickEvent() = 0;
+    virtual void dispatchShowEvent() = 0;
+    virtual void dispatchErrorEvent() = 0;
+    virtual void dispatchCloseEvent() = 0;
+};
+
+} // namespace blink
+
+#endif // WebNotificationDelegate_h