FolderImage: Const correctness.

ui/app_list/folder_image.h

 // Copyright 2014 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_FOLDER_IMAGE_H_
 #define UI_APP_LIST_FOLDER_IMAGE_H_
 
 #include <vector>
 
 #include "base/observer_list.h"
@@ skipping 29 matching lines @@
   explicit FolderImage(AppListItemList* item_list);
   ~FolderImage() override;
 
   // Generates the folder's icon from the icons of the items in the item list,
   // and notifies observers that the icon has changed.
   void UpdateIcon();
 
   const gfx::ImageSkia& icon() const { return icon_; }
 
   // Returns the icon of one of the top items with |item_index|.
-  const gfx::ImageSkia& GetTopIcon(size_t item_index);
+  const gfx::ImageSkia& GetTopIcon(size_t item_index) const;
 
   // Calculates the top item icons' bounds inside |folder_icon_bounds|.
   // Returns the bounds of top item icons in sequence of top left, top right,
   // bottom left, bottom right.
   static std::vector<gfx::Rect> GetTopIconsBounds(
       const gfx::Rect& folder_icon_bounds);
 
   // Returns the target icon bounds for |item| to fly back to its parent folder
   // icon in animation UI. If |item| is one of the top item icon, this will
   // match its corresponding top item icon in the folder icon. Otherwise,
   // the target icon bounds is centered at the |folder_icon_bounds| with
   // the same size of the top item icon.
   // The Rect returned is in the same coordinates of |folder_icon_bounds|.
   gfx::Rect GetTargetIconRectInFolderForItem(
       AppListItem* item,
-      const gfx::Rect& folder_icon_bounds);
+      const gfx::Rect& folder_icon_bounds) const;
 
   void AddObserver(FolderImageObserver* observer);
   void RemoveObserver(FolderImageObserver* observer);
 
   // AppListItemObserver overrides:
   void ItemIconChanged() override;
 
   // AppListItemListObserver overrides:
   void OnListItemAdded(size_t index, AppListItem* item) override;
   void OnListItemRemoved(size_t index, AppListItem* item) override;
@@ skipping 15 matching lines @@
 
   // Top items for generating folder icon.
   std::vector<AppListItem*> top_items_;
 
   ObserverList<FolderImageObserver> observers_;
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_FOLDER_IMAGE_H_