It's not really what you asked for, but subtitles that you download from websites like zimuku.com or zimuku.cn have dual language versions: separate English and Chinese flag means the ZIP file contains separate language subs, pirate flag means it has one set of subtitles containing both languages - super useful if your video player doesn't support displaying more than one set or you don't want subs at the top of the screen).

Just tried the extension, and it seems Pinyin is not supported. There is no "Transliteration" option, like there is for Japanese.