athena: Expose the list of activities from the ActivityManager.

athena/test/base/activity_lifetime_tracker.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_TEST_BASE_ACTIVITY_LIFETIME_TRACKER_H_
 #define ATHENA_TEST_BASE_ACTIVITY_LIFETIME_TRACKER_H_
 
 #include "athena/activity/public/activity_manager_observer.h"
 #include "base/macros.h"
 
 namespace athena {
 class Activity;
 
 // Listens for activities to be started / ended and will return them.
 class ActivityLifetimeTracker : public ActivityManagerObserver {
  public:
   ActivityLifetimeTracker();
   ~ActivityLifetimeTracker() override;
 
-  // Called after an |activity| got created.
+  // ActivityManagerObserver:
   void OnActivityStarted(Activity* activity) override;
-
-  // Called before an |activity| gets destroyed.
   void OnActivityEnding(Activity* activity) override;
+  void OnActivityOrderChanged() override;
 
   // Returns the newly created activity (if any) and resets its reference.
   Activity* GetNewActivityAndReset();
 
   // Returns a deleted activity (if any) and resets its reference.
   // Note that the pointer is void* since the Activity was deleted when
   // requested.
   void* GetDeletedActivityAndReset();
 
  private:
   // The activity which got created if not nullptr.
   Activity* new_activity_;
 
   // An old activity which got unloaded if not nullptr.
   void* deleted_activity_;
 
   DISALLOW_COPY_AND_ASSIGN(ActivityLifetimeTracker);
 };
 
 }  // namespace athena
 
 #endif //  ATHENA_TEST_BASE_ACTIVITY_LIFETIME_TRACKER_H_