exo: Implement notification surface support

components/exo/notification_surface_manager.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 COMPONENTS_EXO_NOTIFICATION_SURFACE_MANAGER_H_
+#define COMPONENTS_EXO_NOTIFICATION_SURFACE_MANAGER_H_
+
+#include <string>
+
+namespace exo {
+
+class NotificationSurface;
+
+class NotificationSurfaceManager {
+ public:
+  // Gets the NotificationSurface associated with the given notification id.
+  // Returns nullptr if no NotificationSurface is associated with the id.
+  virtual NotificationSurface* GetSurface(
+      const std::string& notification_id) const = 0;
+
+  // Adds a NotificationSurface to the manager.
+  virtual void AddSurface(NotificationSurface* surface) = 0;
+
+  // Removes a NotificationSurface from the manager.
+  virtual void RemoveSurface(NotificationSurface* surface) = 0;
+
+ protected:
+  virtual ~NotificationSurfaceManager() {}
+};
+
+}  // namespace exo
+
+#endif  // COMPONENTS_EXO_NOTIFICATION_SURFACE_MANAGER_H_