App list uses PaginationModel to transition between pages.

ui/app_list/pagination_model.h

Index: ui/app_list/pagination_model.h
diff --git a/ui/app_list/pagination_model.h b/ui/app_list/pagination_model.h
index 0546adc4bf894573f1d95ab5994e94d56eeed7d5..3abb71488cbd4ab314b69e739d7abe3dce7739b6 100644
--- a/ui/app_list/pagination_model.h
+++ b/ui/app_list/pagination_model.h
@@ -93,6 +93,10 @@ class APP_LIST_EXPORT PaginationModel : public gfx::AnimationDelegate {
     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();