[css-writing-mode]Direction and writing-mode on table rows/row-groups etc.

Hi,

I just tried http://output.jsbin.com/cufubiv on Firefox which supports
logical properties to see how 'direction' and 'writing-mode' on TBODY are
handled, and I summarize as below:
- The properties affect logical styles;
- The properties don't affect order of table rows and columns;
- The properties are inherited by descendants;

I think Firefox's behavior is reasonable, but it would be better if the
spec defined it more precisely. For example, we may need clarification
about the applicability of 'writing-mode' (which is currently described as
not applicable to table-row-groups, etc.), and how 'direction' (which is
described as applicable to all elements) on table-row-groups etc. affects
column order.

Thanks,
Xianzhu