athena: Expose the list of activities from the ActivityManager.

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 <vector>
+
 #include "athena/athena_export.h"
 
 namespace aura {
 class Window;
 }
 
 namespace athena {
 
 class Activity;
 class ActivityManagerObserver;
 
+using ActivityList = std::vector<Activity*>;
+
 // Manages a set of activities.
 class ATHENA_EXPORT ActivityManager {
  public:
   static ActivityManager* Create();
   static ActivityManager* Get();
   static void Shutdown();
 
   virtual ~ActivityManager() {}
 
   // Adds/Removes an activity. ActivityManager owns the activities.
   virtual void AddActivity(Activity* activity) = 0;
   virtual void RemoveActivity(Activity* activity) = 0;
 
+  // Updates the UI when the task color/title changes.
+  virtual void UpdateActivity(Activity* activity) = 0;
+
+  // Returns a list of activities, sorted in their activation order (the most
+  // recently used activity is at the front of the returned list).
+  virtual const ActivityList& GetActivityList() = 0;
+
   // Returns the activity that has a |window| as toplevel window, or
   // nullptr if such activity does not exist.
   virtual Activity* GetActivityForWindow(aura::Window* window) = 0;
 
-  // Updates the UI when the task color/title changes.
-  virtual void UpdateActivity(Activity* activity) = 0;
-
   virtual void AddObserver(ActivityManagerObserver* observer) = 0;
   virtual void RemoveObserver(ActivityManagerObserver* observer) = 0;
 };
 
 }  // namespace athena
 
 #endif  // ATHENA_ACTIVITY_PUBLIC_ACTIVITY_MANAGER_H_