Move handler processing to NotificationDisplayService

chrome/browser/notifications/notification_handler.h

 // Copyright 2016 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 CHROME_BROWSER_NOTIFICATIONS_NOTIFICATION_HANDLER_H_
 #define CHROME_BROWSER_NOTIFICATIONS_NOTIFICATION_HANDLER_H_
 
 #include <memory>
 #include <string>
 
 namespace base {
 class NullableString16;
 }
 
 class Profile;
 
 // Interface that enables the different kind of notifications to process
-// operations coming from the user.
+// operations coming from the user or decisions made by the underlying
+// notification type.
 class NotificationHandler {
  public:
   virtual ~NotificationHandler() {}
 
+  virtual void OnShow(Profile* profile, const std::string& notification_id) = 0;
+
   // Process notification close events.
   virtual void OnClose(Profile* profile,
                        const std::string& origin,
                        const std::string& notification_id,
                        bool by_user) = 0;
 
   // Process cliks to a notification or its buttons, depending on
   // |action_index|.
   virtual void OnClick(Profile* profile,
                        const std::string& origin,
                        const std::string& notification_id,
                        int action_index,
                        const base::NullableString16& reply) = 0;
 
   // Open notification settings.
   virtual void OpenSettings(Profile* profile) = 0;
 };
 
 #endif  // CHROME_BROWSER_NOTIFICATIONS_NOTIFICATION_HANDLER_H_