Add NotificationDisplayServiceProxy

chrome/browser/notifications/notification_platform_bridge_linux.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 CHROME_BROWSER_NOTIFICATIONS_NOTIFICATION_PLATFORM_BRIDGE_LINUX_H_
 #define CHROME_BROWSER_NOTIFICATIONS_NOTIFICATION_PLATFORM_BRIDGE_LINUX_H_
 
 #include <unordered_map>
 
 #include "base/macros.h"
@@ skipping 11 matching lines @@
                const std::string& profile_id,
                bool is_incognito,
                const Notification& notification) override;
   void Close(const std::string& profile_id,
              const std::string& notification_id) override;
   void GetDisplayed(
       const std::string& profile_id,
       bool incognito,
       const GetDisplayedNotificationsCallback& callback) const override;
 
-  // Waits until the D-Bus connection has been created.  Returns true
-  // if the connection was successful.
-  bool BlockUntilReady();
+  void IsConnected(const base::Callback<void(bool)>& callback);
 
  private:
   class NativeNotificationThread;
 
   std::unique_ptr<NativeNotificationThread> thread_;
 
   DISALLOW_COPY_AND_ASSIGN(NotificationPlatformBridgeLinux);
 };
 
 #endif  // CHROME_BROWSER_NOTIFICATIONS_NOTIFICATION_PLATFORM_BRIDGE_LINUX_H_