Vertically centered app list page switcher

ui/app_list/views/page_switcher.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_PAGE_SWITCHER_H_
 #define UI_APP_LIST_VIEWS_PAGE_SWITCHER_H_
 
-#include "base/macros.h"
-#include "ui/app_list/pagination_model_observer.h"
-#include "ui/views/controls/button/button.h"
 #include "ui/views/view.h"
 
 namespace app_list {
 
-class PaginationModel;
-
 // PageSwitcher represents its underlying PaginationModel with a button strip.
 // Each page in the PageinationModel has a button in the strip and when the
 // button is clicked, the corresponding page becomes selected.
-class PageSwitcher : public views::View,
-                     public views::ButtonListener,
-                     public PaginationModelObserver {
+class PageSwitcher : public views::View {
  public:
-  explicit PageSwitcher(PaginationModel* model);
-  ~PageSwitcher() override;
-
   // Returns the page index of the page switcher button under the point. If no
   // page switcher button is under the point, -1 is return. |point| is in
   // PageSwitcher's coordinates.
-  int GetPageForPoint(const gfx::Point& point) const;
+  virtual int GetPageForPoint(const gfx::Point& point) const = 0;
 
   // Shows hover for button under the point. |point| is in PageSwitcher's
   // coordinates.
-  void UpdateUIForDragPoint(const gfx::Point& point);
-
-  // Overridden from views::View:
-  gfx::Size CalculatePreferredSize() const override;
-  void Layout() override;
-
- private:
-  void CalculateButtonWidthAndSpacing(int contents_width);
-
-  // Overridden from views::ButtonListener:
-  void ButtonPressed(views::Button* sender, const ui::Event& event) override;
-
-  // Overridden from PaginationModelObserver:
-  void TotalPagesChanged() override;
-  void SelectedPageChanged(int old_selected, int new_selected) override;
-  void TransitionStarted() override;
-  void TransitionChanged() override;
-
-  PaginationModel* model_;  // Owned by AppsGridView.
-  views::View* buttons_;  // Owned by views hierarchy.
-
-  DISALLOW_COPY_AND_ASSIGN(PageSwitcher);
+  virtual void UpdateUIForDragPoint(const gfx::Point& point) = 0;
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_VIEWS_PAGE_SWITCHER_H_