[css-step-sizing] Offline spec review in Tokyo

JFYI, Hiroshi hosted an offline spec review session for CSS Step Sizing in
Tokyo today. Florian, Murakami-san, Hiroshi, Baba-san, and a couple of more
from BPS, Hiroshi's company joined the session.

Most of over 2 hours of the session were spent on Q&A for the better mutual
understanding. There were some good feedback too and attendees said they
will send the feedback to www-style.

So much thank you to Hiroshi for hosting and to all attendees for pointing
out how bad my communication was ;) we solved several misunderstanding and
I hope the session helps more active discussions at this ML and the WG.

/koji