FolderImage: Const correctness.

BUG=425444

Review URL: https://codereview.chromium.org/953743003

Cr-Commit-Position: refs/heads/master@{#317991}

ui/app_list/folder_image.cc

@@ -132,7 +132,7 @@ void FolderImage::UpdateIcon() {
   RedrawIconAndNotify();
 }
 
-const gfx::ImageSkia& FolderImage::GetTopIcon(size_t item_index) {
+const gfx::ImageSkia& FolderImage::GetTopIcon(size_t item_index) const {
   CHECK_LT(item_index, top_items_.size());
   return top_items_[item_index]->icon();
 }
@@ -171,7 +171,7 @@ std::vector<gfx::Rect> FolderImage::GetTopIconsBounds(
 
 gfx::Rect FolderImage::GetTargetIconRectInFolderForItem(
     AppListItem* item,
-    const gfx::Rect& folder_icon_bounds) {
+    const gfx::Rect& folder_icon_bounds) const {
   for (size_t i = 0; i < top_items_.size(); ++i) {
     if (item->id() == top_items_[i]->id()) {
       std::vector<gfx::Rect> rects = GetTopIconsBounds(folder_icon_bounds);

ui/app_list/folder_image.h

@@ -47,7 +47,7 @@ class APP_LIST_EXPORT FolderImage : public AppListItemListObserver,
   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,
@@ -63,7 +63,7 @@ class APP_LIST_EXPORT FolderImage : public AppListItemListObserver,
   // 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);