Share session/cookie between subdomains for Play 2.X

I only can find Play 1.x has this setting. How to set this in Play 2.X?

http://www.playframework.org/documentation/1.2.4/configuration

application.defaultCookieDomain

Enables session/cookie sharing between subdomains. For example, to make cookies valid for all domains ending with ‘.example.com’, e.g. foo.example.com and bar.example.com:

application.defaultCookieDomain=.example.com Default: a cookie is only valid for a specific domain.