コピー&ペーストなどの特別なコマンドを検証
"Copy", "Cut", "Paste", "Delete", "FrameSelected", "Duplicate", "SelectAll" and so on.
Sent only in the editor.
例:現在のウィンドウやコントロールで行ったペースト
    function OnGUI()
    {
        var e:Event = Event.current;
        if (e.type == EventType.ValidateCommand && e.commandName == "Paste")
        {
            Debug.Log("validate paste");
            e.Use(); // without this line we won't get ExecuteCommand
        }
        if (e.type == EventType.ExecuteCommand && e.commandName == "Paste")
        {
            Debug.Log("Pasting: " + EditorGUIUtility.systemCopyBuffer);
        }
    }