Reported by Peter Moulder, David Baron
10.5 (Content height: the 'height' property) [http://www.w3.org/TR/CSS21/visudet.html#propdef-height] says:
# Computed value: the percentage or 'auto' (see prose under
# <percentage>) or the absolute length
# [...] If the height of the containing block is not
# specified explicitly (i.e., it depends on content height),
# and this element is not absolutely positioned, the value
# computes to 'auto'.
Some implementers want the computed value to remain a percentage and just have the used value be 'auto', since the rule as given constrains implementations to implement the concept of containing block in terms of style data rather than in terms of the rendering tree, which is a significant constraint on implementation modularity.
I described the implementor request incorrectly; the used value would not be 'auto' it would be a length. Hence the request is that % height inside of auto-height container should result in % computed value but used value is determined as if computed value were 'auto'.
In the computed value line, replace
# (see prose under <percentage>)
| (as specified)
In the <percentage> definition, replace
| the value computes to 'auto'
| the used height is calculated as if 'auto' was specified
The text assert of such tests would have to be updated if proposed changes are adopted.