Refactor app list scrolling: introduce the PaginationController class.

ui/app_list/views/apps_grid_view.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_VIEWS_APPS_GRID_VIEW_H_
 #define UI_APP_LIST_VIEWS_APPS_GRID_VIEW_H_
 
 #include <set>
 #include <string>
 
@@ skipping 32 matching lines @@
 
 namespace test {
 class AppsGridViewTestApi;
 }
 
 class ApplicationDragAndDropHost;
 class AppListItemView;
 class AppsGridViewDelegate;
 class AppsGridViewFolderDelegate;
 class PageSwitcher;
-class PaginationModel;
+class PaginationController;
 
 // AppsGridView displays a grid for AppListItemList sub model.
 class APP_LIST_EXPORT AppsGridView : public views::View,
                                      public views::ButtonListener,
                                      public AppListItemListObserver,
                                      public PaginationModelObserver,
                                      public AppListModelObserver,
                                      public ui::ImplicitAnimationObserver {
  public:
   enum Pointer {
@@ skipping 153 matching lines @@
 
  private:
   friend class test::AppsGridViewTestApi;
 
   enum DropAttempt {
     DROP_FOR_NONE,
     DROP_FOR_REORDER,
     DROP_FOR_FOLDER,
   };
 
-  enum ScrollAxis { SCROLL_AXIS_HORIZONTAL, SCROLL_AXIS_VERTICAL };
-
   // Represents the index to an item view in the grid.
   struct Index {
     Index() : page(-1), slot(-1) {}
     Index(int page, int slot) : page(page), slot(slot) {}
 
     bool operator==(const Index& other) const {
       return page == other.page && slot == other.slot;
     }
     bool operator!=(const Index& other) const {
       return page != other.page || slot != other.slot;
@@ skipping 215 matching lines @@
   bool IsUnderOEMFolder();
 
   void StartSettingUpSynchronousDrag();
   bool RunSynchronousDrag();
   void CleanUpSynchronousDrag();
 #if defined(OS_WIN)
   void OnGotShortcutPath(scoped_refptr<SynchronousDrag> drag,
                          const base::FilePath& path);
 #endif
 
-  // Determines whether the grid view scrolls horizontally or vertically.
-  static ScrollAxis GetScrollAxis();
-
   AppListModel* model_;  // Owned by AppListView.
   AppListItemList* item_list_;  // Not owned.
   AppsGridViewDelegate* delegate_;
 
   // This can be NULL. Only grid views inside folders have a folder delegate.
   AppsGridViewFolderDelegate* folder_delegate_;
 
   PaginationModel pagination_model_;
+  // Must appear after |pagination_model_|.
+  scoped_ptr<PaginationController> pagination_controller_;
   PageSwitcher* page_switcher_view_;  // Owned by views hierarchy.
 
   int cols_;
   int rows_per_page_;
 
   // Tracks app item views. There is a view per item in |model_|.
   views::ViewModel view_model_;
 
   // Tracks pulsing block views.
   views::ViewModel pulsing_blocks_model_;
@@ skipping 71 matching lines @@
 
   // True if the drag_view_ item is a folder item being dragged for reparenting.
   bool dragging_for_reparent_item_;
 
   DISALLOW_COPY_AND_ASSIGN(AppsGridView);
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_VIEWS_APPS_GRID_VIEW_H_