Implement app list folder management page UI.

ui/app_list/views/contents_view.h

Index: ui/app_list/views/contents_view.h
diff --git a/ui/app_list/views/contents_view.h b/ui/app_list/views/contents_view.h
index 4c2c6fef6a10c7fcc4b1765f3d676625814f2948..c9acaaa8245bdcbae7e6dd25c17fe0733bef012b 100644
--- a/ui/app_list/views/contents_view.h
+++ b/ui/app_list/views/contents_view.h
@@ -23,6 +23,7 @@ namespace app_list {
 
 class AppsGridView;
 class ApplicationDragAndDropHost;
+class AppListFolderItem;
 class AppListMainView;
 class AppListModel;
 class AppListViewDelegate;
@@ -49,6 +50,8 @@ class ContentsView : public views::View {
       ApplicationDragAndDropHost* drag_and_drop_host);
 
   void ShowSearchResults(bool show);
+  void ShowFolderContent(AppListFolderItem* folder);
+  void ShowApps();
 
   void Prerender();
 
@@ -56,6 +59,7 @@ class ContentsView : public views::View {
   enum ShowState {
     SHOW_APPS,
     SHOW_SEARCH_RESULTS,
+    SHOW_FOLDER_CONTENT,
   };
 
   // Sets show state.
@@ -78,6 +82,7 @@ class ContentsView : public views::View {
   virtual void OnScrollEvent(ui::ScrollEvent* event) OVERRIDE;
 
   ShowState show_state_;
+  ShowState previous_show_state_;
   PaginationModel* pagination_model_;  // Owned by AppListController.
 
   AppsGridView* apps_grid_view_;  // Owned by the view.