Implement PermissionService::GetNextPermissionChange.

chrome/browser/content_settings/permission_observer.h

+// Copyright 2015 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_CONTENT_SETTINGS_PERMISSION_OBSERVER_H_
+#define CHROME_BROWSER_CONTENT_SETTINGS_PERMISSION_OBSERVER_H_
+
+#include "base/callback.h"
+#include "base/id_map.h"
+#include "base/macros.h"
+#include "components/content_settings/core/browser/content_settings_observer.h"
+#include "components/content_settings/core/common/content_settings.h"
+#include "components/keyed_service/core/keyed_service.h"
+
+class Profile;
+
+class PermissionObserver : public KeyedService,
+                           public content_settings::Observer {
+ public:
+  using PermissionChangeCallback = base::Callback<void(ContentSetting)>;
+
+  explicit PermissionObserver(Profile* profile);
+  ~PermissionObserver() override;
+
+  int Subscribe(ContentSettingsType content_type,
+                const GURL& requesting_origin,
+                const GURL& embedding_origin,
+                const PermissionChangeCallback& callback);
+  void Unsubscribe(int subscription_id);
+
+ private:
+  struct Subscription;
+  using SubscriptionsMap = IDMap<Subscription, IDMapOwnPointer>;
+
+  // content_settings::Observer implementation.
+  void OnContentSettingChanged(const ContentSettingsPattern& primary_pattern,
+                               const ContentSettingsPattern& secondary_pattern,
+                               ContentSettingsType content_type,
+                               std::string resource_identifier) override;
+
+  Profile* profile_;
+  SubscriptionsMap subscriptions_;
+
+  DISALLOW_COPY_AND_ASSIGN(PermissionObserver);
+};
+
+#endif // CHROME_BROWSER_CONTENT_SETTINGS_PERMISSION_OBSERVER_H_