ui/base/models: Make ComboboxModel::GetItemCount() a constant function.

chrome/browser/bookmarks/recently_used_folders_combo_model.h

Index: chrome/browser/bookmarks/recently_used_folders_combo_model.h
diff --git a/chrome/browser/bookmarks/recently_used_folders_combo_model.h b/chrome/browser/bookmarks/recently_used_folders_combo_model.h
index 94118650fde8166231fe7c932b35d827a89fcafc..e1a1cc736dc4fe3a35abff8ba35da8c42eb284eb 100644
--- a/chrome/browser/bookmarks/recently_used_folders_combo_model.h
+++ b/chrome/browser/bookmarks/recently_used_folders_combo_model.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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.
 
@@ -21,7 +21,7 @@ class RecentlyUsedFoldersComboModel : public ui::ComboboxModel {
   virtual ~RecentlyUsedFoldersComboModel();
 
   // Overridden from ui::ComboboxModel:
-  virtual int GetItemCount() OVERRIDE;
+  virtual int GetItemCount() const OVERRIDE;
   virtual string16 GetItemAt(int index) OVERRIDE;
 
   // Returns the node at the specified |index|.