Refactor app list so AppsGridView owns the PaginationModel.

ui/app_list/views/page_switcher.h

Index: ui/app_list/views/page_switcher.h
diff --git a/ui/app_list/views/page_switcher.h b/ui/app_list/views/page_switcher.h
index 61a00ae64ce071f4c3cc181591322cce11747352..9f056129e7ca20f81207f00c71ef586a70c31980 100644
--- a/ui/app_list/views/page_switcher.h
+++ b/ui/app_list/views/page_switcher.h
@@ -33,6 +33,10 @@ class PageSwitcher : public views::View,
   // coordinates.
   void UpdateUIForDragPoint(const gfx::Point& point);
 
+  // Disconnects the PageSwitcher from its underlying PaginationModel. Can be
+  // used if the PaginationModel is going to be destroyed.
+  void ReleasePaginationModel();
+
   // Overridden from views::View:
   virtual gfx::Size GetPreferredSize() const OVERRIDE;
   virtual void Layout() OVERRIDE;
@@ -50,7 +54,7 @@ class PageSwitcher : public views::View,
   virtual void TransitionStarted() OVERRIDE;
   virtual void TransitionChanged() OVERRIDE;
 
-  PaginationModel* model_;  // Owned by AppListController.
+  PaginationModel* model_;  // Owned by AppsGridView; may be NULL.
   views::View* buttons_;  // Owned by views hierarchy.
 
   DISALLOW_COPY_AND_ASSIGN(PageSwitcher);