App list uses PaginationModel to transition between pages.

ui/app_list/pagination_model.h

 // Copyright (c) 2012 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 UI_APP_LIST_PAGINATION_MODEL_H_
 #define UI_APP_LIST_PAGINATION_MODEL_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 75 matching lines @@
   const Transition& transition() const { return transition_; }
 
   bool is_valid_page(int page) const {
     return page >= 0 && page < total_pages_;
   }
 
   bool has_transition() const {
     return transition_.target_page != -1 || transition_.progress != 0;
   }
 
+  // Gets the page that the animation will eventually land on. If there is no
+  // active animation, just returns selected_page().
+  int SelectedTargetPage() const;
+
  private:
   void NotifySelectedPageChanged(int old_selected, int new_selected);
   void NotifyTransitionStarted();
   void NotifyTransitionChanged();
 
   void clear_transition() {
     SetTransition(Transition(-1, 0));
   }
 
   // Calculates a target page number by combining current page and |delta|.
@@ skipping 29 matching lines @@
   base::TimeTicks last_overscroll_animation_start_time_;
 
   ObserverList<PaginationModelObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(PaginationModel);
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_PAGINATION_MODEL_H_