[CSS21][css-text] percentages on text-indent

From a side discussion with Greg Whitworth at the face-to-face
meeting (triggered by Greg pointing out
https://twitter.com/HugoGiraudel/status/565093151904645120 ):

Looking at either:
  http://dev.w3.org/csswg/css2/text.html#indentation-prop
  http://dev.w3.org/csswg/css-text/#text-indent-property
it's not clear what percentages on text-indent mean.

It says that percentages refer to the width of the containing block:
but is that the containing block of the line with the text, or the
containing block of the block to which text-indent applies (i.e.,
the first block's containing block)?

Apparently browsers disagree on this.  Making the spec's wording
more precise seems likely to help.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                          https://www.mozilla.org/   𝄂
             Before I built a wall I'd ask to know
             What I was walling in or walling out,
             And to whom I was like to give offense.
               - Robert Frost, Mending Wall (1914)