exo: Implement notification surface support

components/exo/notification_surface_registry.cc

+// 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.
+
+#include "components/exo/notification_surface_registry.h"
+
+#include <algorithm>
+
+#include "components/exo/notification_surface.h"
+
+namespace exo {
+
+NotificationSurfaceRegistry::NotificationSurfaceRegistry() {}
+
+NotificationSurfaceRegistry::~NotificationSurfaceRegistry() {}
+
+NotificationSurface* NotificationSurfaceRegistry::GetSurface(
+    const std::string& notification_key) const {
+  auto it = notification_surface_map_.find(notification_key);
+  return it == notification_surface_map_.end() ? nullptr : it->second;
+}
+
+void NotificationSurfaceRegistry::AddSurface(NotificationSurface* surface) {
+  if (notification_surface_map_.find(surface->notification_id()) !=
+      notification_surface_map_.end()) {
+    NOTREACHED();
+    return;
+  }
+
+  notification_surface_map_[surface->notification_id()] = surface;
+
+  FOR_EACH_OBSERVER(Observer, observers_, OnNotificationSurfaceAdded(surface));
+}
+
+void NotificationSurfaceRegistry::RemoveSurface(NotificationSurface* surface) {
+  auto it = notification_surface_map_.find(surface->notification_id());
+  if (it == notification_surface_map_.end())
+    return;
+
+  notification_surface_map_.erase(it);
+  FOR_EACH_OBSERVER(Observer, observers_,
+                    OnNotificationSurfaceRemoved(surface));
+}
+
+void NotificationSurfaceRegistry::AddObserver(Observer* observer) {
+  observers_.AddObserver(observer);
+}
+
+void NotificationSurfaceRegistry::RemoveObserver(Observer* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+}  // namespace exo