add: case "cmd_undo": case "cmd_redo":   return true;  
context: 	isCommandEnabled: function(command)	{		dump("ThreadPaneController.isCommandEnabled\n");		switch ( command )		{			case "cmd_selectAll":				return true;						case "cmd_delete":			case "button_delete":				var threadTree = GetThreadTree();				dump("threadTree = " + threadTree + "\n");				var numSelected = 0;				if ( threadTree && threadTree.selectedItems )					numSelected = threadTree.selectedItems.length;				if ( command == "cmd_delete" )				{					if ( numSelected < 2 )						goSetMenuValue(command, 'valueMessage');					else						goSetMenuValue(command, 'valueMessages');				}				return ( numSelected > 0 );						default:				return false;		}	},
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