athena: Add the concept of Activity and related managers.

athena/activity/public/activity_manager.h

+// Copyright 2014 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 ATHENA_ACTIVITY_PUBLIC_ACTIVITY_MANAGER_H_
+#define ATHENA_ACTIVITY_PUBLIC_ACTIVITY_MANAGER_H_
+
+#include "athena/athena_export.h"
+
+namespace athena {
+
+class Activity;
+
+// Manages a set of activities.
+class ATHENA_EXPORT ActivityManager {
+ public:
+  static ActivityManager* Create();
+  static ActivityManager* Get();
+  static void Shutdown();
+
+  virtual ~ActivityManager() {}
+
+  // Adds/Removes a task.
+  virtual void AddActivity(Activity* task) = 0;
+  virtual void RemoveActivity(Activity* task) = 0;
+
+  // Updates the UI when the task color/title changes.
+  virtual void UpdateActivity(Activity* task) = 0;
+};
+
+}  // namespace athena
+
+#endif  // ATHENA_ACTIVITY_PUBLIC_ACTIVITY_MANAGER_H_