[Media Router] Connection state change listening redesign part 2.

chrome/browser/media/router/media_router_base.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_MEDIA_ROUTER_MEDIA_ROUTER_BASE_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_BASE_H_
+
+#include "base/callback_list.h"
+#include "base/containers/scoped_ptr_hash_map.h"
+#include "base/macros.h"
+#include "base/threading/thread_checker.h"
+#include "chrome/browser/media/router/media_router.h"
+
+namespace media_router {
+
+class MediaRouterBase : public MediaRouter {
+ public:
+  MediaRouterBase();
+  ~MediaRouterBase() override;
+
+  scoped_ptr<PresentationConnectionStateSubscription>
+  AddPresentationConnectionStateChangedCallback(
+      const MediaRoute::Id& route_id,
+      const content::PresentationConnectionStateChangedCallback& callback)
+      override;
+
+ protected:
+  void NotifyPresentationConnectionStateChange(
+      const MediaRoute::Id& route_id,
+      content::PresentationConnectionState state);
+
+  using PresentationConnectionStateChangedCallbacks =
+      base::CallbackList<void(content::PresentationConnectionState)>;
+  base::ScopedPtrHashMap<
+      MediaRoute::Id,
+      scoped_ptr<PresentationConnectionStateChangedCallbacks>>
+      presentation_connection_state_callbacks_;
+
+  base::ThreadChecker thread_checker_;
+
+ private:
+  // Called when a PresentationConnectionStateChangedCallback associated with
+  // |route_id| is removed from |presentation_connection_state_callbacks_|.
+  void OnPresentationConnectionStateCallbackRemoved(
+      const MediaRoute::Id& route_id);
+
+  DISALLOW_COPY_AND_ASSIGN(MediaRouterBase);
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_BASE_H_