The Mac wrench menu zoom controls honor the global enabled state of the zoom commands.

app/menus/button_menu_item_model.h

Index: app/menus/button_menu_item_model.h
diff --git a/app/menus/button_menu_item_model.h b/app/menus/button_menu_item_model.h
index 29a8b7c409b57ef8811511b449b2e69d8ba74cc6..8e3300ea522cee6d0e4a3dbaefc65d6c18061dec 100644
--- a/app/menus/button_menu_item_model.h
+++ b/app/menus/button_menu_item_model.h
@@ -31,6 +31,7 @@ class ButtonMenuItemModel {
 
     // Performs the action associated with the specified command id.
     virtual void ExecuteCommand(int command_id) = 0;
+    virtual bool IsCommandIdEnabled(int command_id) const { return true; }
   };
 
   ButtonMenuItemModel(int string_id, ButtonMenuItemModel::Delegate* delegate);
@@ -77,6 +78,9 @@ class ButtonMenuItemModel {
   // Called from implementations.
   void ActivatedCommand(int command_id);
 
+  // Returns the enabled state of the button at |index|.
+  bool IsEnabledAt(int index) const;
+
   const string16& label() const { return item_label_; }
 
  private: