athena: Use ActivityList where appropriate, and fix AppActivity tests.

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/activity/public/activity.h"
 #include "athena/athena_export.h"
+#include "base/memory/scoped_ptr.h"
 
 namespace aura {
 class Window;
 }
 
 namespace athena {
 
 class Activity;
 class ActivityManagerObserver;
 
+struct ActivityDeleter {
+  inline void operator()(Activity* activity) const {
+    Activity::Delete(activity);
+  }
+};
+
 using ActivityList = std::vector<Activity*>;
+using ScopedActivity = scoped_ptr<Activity, ActivityDeleter>;
 
 // 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;
 
+  virtual ScopedActivity ReplaceActivity(Activity* to_replace,
+                                         Activity* replace_with) = 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;
 
   virtual void AddObserver(ActivityManagerObserver* observer) = 0;
   virtual void RemoveObserver(ActivityManagerObserver* observer) = 0;
 };
 
 }  // namespace athena
 
 #endif  // ATHENA_ACTIVITY_PUBLIC_ACTIVITY_MANAGER_H_