Simplified or traditional for each Chinese macrolanguage

Hi,

A bug was filed to Blink[1] saying it doesn't pick appropriate fonts for
Yue, Wu, and other Chinese. A similar bug is also found in Gecko for Yue[2]
and Wu[3].

To pick appropriate fonts, browsers need to know whether traditional or
simplified is preferred for the language, and I believe it's the same for
Gecko.

Yue looks easy, all information I looked for says traditional. Wu is a
little harder, but IIUC it looks like the majority is simplified, so
probably the correct thing is to map "wuu" and "zh-wuu" to simplified,
while "wuu-hant" and "zh-hant-wuu" to traditional.

Now, ISO says there are 14 languages in Chinese macrolanguage[4].

Would it be possible to provide a guidance of whether browsers should pick
simplified or traditional for each Chinese macrolanguge?

[1] https://crbug.com/611817
[2] https://bugzilla.mozilla.org/show_bug.cgi?id=484191
[3] https://bugzilla.mozilla.org/show_bug.cgi?id=1244404
[4] http://www-01.sil.org/iso639-3/documentation.asp?id=zho

/koji