def find_bookmark_file ():
    """Return the bookmark file of the Default profile.
    Returns absolute filename if found, or empty string if no bookmark file
    could be found.
    """
    if sys.platform != 'darwin':
        return u""
    try:
        dirname = get_profile_dir()
        if os.path.isdir(dirname):
            fname = os.path.join(dirname, u"Bookmarks.plist")
            if os.path.isfile(fname):
                return fname
    except Exception:
        pass
    return u""
Return the bookmark file of the Default profile.
    Returns absolute filename if found, or empty string if no bookmark file
    could be found.