Introduce a new API to handle native notification clicks

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>
+
+#include "chrome/browser/notifications/notification_operation_common.h"
+
+class Notification;
+class Profile;
+
+// Interface that enables the different kind of notifications
+// to process operations coming from the user.
+// Whenever a notification is clicked or closed or a button is pressed
+// the right kind of NotificationHandler will deal with the operation.
+class NotificationHandler {
+ public:
+  virtual ~NotificationHandler() {}
+
+  // Handles a given |operation|, click, close etc.
+  // This is only meant for user initiated actions.
+  // For a notification with |notification_id| and a certain |profile|.
+  virtual void HandleNotificationOperation(
+      notification_operation_common::NotificationOperation operation,

[Peter Beverloo, 2016/06/29 00:23:16]

Could we instead just have multiple methods on the NotificationHandler
interface?

OnClick(Profile* profile, const std::string& origin,
        const std::string& notification_id, int action_index);
OnSettingsClick(Profile* profile, const std::string& origin,
                const std::string& notification_id);
OnClose(Profile* profile, const std::string& origin,
        const std::string& notification_id);

(Do they all need all this information?)

[Miguel Garcia, 2016/07/05 13:54:50]

Done.

+      Profile* profile,
+      const std::string& origin,
+      const std::string& notification_id,
+      int action_index) = 0;
+
+  // Registers a |Notification| object with this handler.
+  virtual void RegisterNotification(

[Peter Beverloo, 2016/06/29 00:23:16]

This should be the displayer's responsibility. For example, for persistent
notifications we would now always allocate a Notification object, which gets
destroyed immediately because the handler doesn't need it.

[Miguel Garcia, 2016/07/05 13:54:50]

As agreed offline I moved to only storing the delegates so we don't create
useless notification objects.

+      const std::string& notification_id,
+      std::unique_ptr<Notification> notification) = 0;
+
+  // Meant for programatically closed notification.
+  virtual void CloseNotification(Profile* profile,

[Peter Beverloo, 2016/06/29 00:23:16]

This should be a |by_user| boolean flag in the `OnClose` method, presumably?

[Miguel Garcia, 2016/07/05 13:54:50]

Done.

+                                 const std::string& notification_id) = 0;
+
+  // Return the kind of notifications the class knows how to handle.
+  virtual notification_operation_common::NotificationHandlerType
+  NotificationType() = 0;
+};
+
+#endif  // CHROME_BROWSER_NOTIFICATIONS_NOTIFICATION_HANDLER_H_