Experimental app list: "All apps" button has a folder-like icon.

ui/app_list/app_list_folder_item.h

Index: ui/app_list/app_list_folder_item.h
diff --git a/ui/app_list/app_list_folder_item.h b/ui/app_list/app_list_folder_item.h
index cd572e71dbba2c43bfad6f7f407c49d72efef12c..5ca5deb3a0eb3830f0850c3e1ab6769b020dc199 100644
--- a/ui/app_list/app_list_folder_item.h
+++ b/ui/app_list/app_list_folder_item.h
@@ -12,8 +12,10 @@
 #include "ui/app_list/app_list_item.h"
 #include "ui/app_list/app_list_item_list_observer.h"
 #include "ui/app_list/app_list_item_observer.h"
+#include "ui/app_list/folder_image.h"
 
 namespace gfx {
+class ImageSkia;
 class Rect;
 }
 
@@ -23,8 +25,7 @@ class AppListItemList;
 
 // AppListFolderItem implements the model/controller for folders.
 class APP_LIST_EXPORT AppListFolderItem : public AppListItem,
-                                          public AppListItemListObserver,
-                                          public AppListItemObserver {
+                                          public FolderImageObserver {
  public:
   // The folder type affects folder behavior.
   enum FolderType {
@@ -39,9 +40,6 @@ class APP_LIST_EXPORT AppListFolderItem : public AppListItem,
   AppListFolderItem(const std::string& id, FolderType folder_type);
   ~AppListFolderItem() override;
 
-  // Updates the folder's icon.
-  void UpdateIcon();
-
   // Returns the icon of one of the top items with |item_index|.
   const gfx::ImageSkia& GetTopIcon(size_t item_index);
 
@@ -57,9 +55,14 @@ class APP_LIST_EXPORT AppListFolderItem : public AppListItem,
   AppListItemList* item_list() { return item_list_.get(); }
   const AppListItemList* item_list() const { return item_list_.get(); }
 
+  // For tests.
+  // TODO(mgiuca): return a const FolderImage& (requires that
+  // base::ObserverList::HasObserver takes a const*).
+  FolderImage* folder_image() { return &folder_image_; }
+
   FolderType folder_type() const { return folder_type_; }
 
-  // AppListItem
+  // AppListItem overrides:
   void Activate(int event_flags) override;
   const char* GetItemType() const override;
   ui::MenuModel* GetContextMenuModel() override;
@@ -71,28 +74,17 @@ class APP_LIST_EXPORT AppListFolderItem : public AppListItem,
   // Returns an id for a new folder.
   static std::string GenerateId();
 
- private:
-  // AppListItemObserver
-  void ItemIconChanged() override;
-
-  // AppListItemListObserver
-  void OnListItemAdded(size_t index, AppListItem* item) override;
-  void OnListItemRemoved(size_t index, AppListItem* item) override;
-  ;
-  void OnListItemMoved(size_t from_index,
-                       size_t to_index,
-                       AppListItem* item) override;
-
-  void UpdateTopItems();
+  // FolderImageObserver overrides:
+  void OnFolderImageUpdated() override;
 
+ private:
   // The type of folder; may affect behavior of folder views.
   const FolderType folder_type_;
 
   // List of items in the folder.
   scoped_ptr<AppListItemList> item_list_;
 
-  // Top items for generating folder icon.
-  std::vector<AppListItem*> top_items_;
+  FolderImage folder_image_;
 
   DISALLOW_COPY_AND_ASSIGN(AppListFolderItem);
 };