[css-ruby] About default style sheet

In my opinion, there are currently two problems in the current default
style sheet: one is the font size of text directly contained by <rtc>, the
other is the line-height, which I mentioned in another thread before.

Since we have changed the spec, and there are use cases where author may
have text inside <rtc> directly, this tag should also have 50% font-size,
or it would be strange when authors try to use span. Considering that <rt>
may be contained inside <rtc>, I propose that this part should be changed
to:

rt, rtc { font-size: 50%; }
rtc > rt { font-size: inherit; }

Then line-height. As in the spec, we encourage authors to specify
sufficient line-height to put annotations, the line-height of <ruby> should
not be "normal" in most cases. But line-height is a property which inherits
by default, which means ruby annotations will inherit the large line-height
from its parent (ruby container). This must not be what authors expect. I
suggest that we break the inheritance for annotations in the default style
sheet, hence:

rt, rtc { line-height: normal; }

or maybe 1em. I'm not sure about what value is better in practice, but
anyway it should not inherit.

- Xidorn