Added default implementations of GetAcceleratorForCommandId.

ui/base/models/button_menu_item_model.h

 // Copyright (c) 2011 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_BASE_MODELS_BUTTON_MENU_ITEM_MODEL_H_
 #define UI_BASE_MODELS_BUTTON_MENU_ITEM_MODEL_H_
 
 #include <vector>
 
 #include "base/macros.h"
@@ skipping 20 matching lines @@
     // Some command ids have labels that change over time.
     virtual bool IsItemForCommandIdDynamic(int command_id) const;
     virtual base::string16 GetLabelForCommandId(int command_id) const;
 
     // Performs the action associated with the specified command id.
     virtual void ExecuteCommand(int command_id, int event_flags) = 0;
     virtual bool IsCommandIdEnabled(int command_id) const;
     virtual bool DoesCommandIdDismissMenu(int command_id) const;
 
     // Gets the accelerator for the specified command id. Returns true if the
-    // command id has a valid accelerator, false otherwise.
-    virtual bool GetAcceleratorForCommandId(
-        int command_id,
-        ui::Accelerator* accelerator) const = 0;
+    // command id has a valid accelerator, false otherwise. By default, returns
+    // false for all commands.
+    virtual bool GetAcceleratorForCommandId(int command_id,
+                                            ui::Accelerator* accelerator) const;
 
    protected:
     virtual ~Delegate() {}
   };
 
   ButtonMenuItemModel(int string_id, ButtonMenuItemModel::Delegate* delegate);
   ~ButtonMenuItemModel();
 
   // Adds a button that will emit |command_id|. All buttons created through
   // this method will have the same size, based on the largest button.
@@ skipping 62 matching lines @@
   std::vector<Item> items_;
 
   Delegate* delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(ButtonMenuItemModel);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_MODELS_BUTTON_MENU_ITEM_MODEL_H_