[css3-flexbox] chunk on line formation doesn't handle flexbox items that are wider than flexbox

Right now, the Flexbox Layout Algorithm chunk on line-breaking doesn't
seem to account for cases where a single flexbox item is larger than the
flexbox's main-size.

The relevant spec text (from the current ED) is:
{{
2. Collect as many consecutive flexbox items as possible, starting from
the first item, while keeping the sum of their margin-box main size
smaller than the flexbox's available space... The items so collected
form a single flexbox line.
3. Repeat the previous step, starting each time from the first flexbox
item not yet collected into a flexbox line, until all flexbox items have
been collected into flexbox lines.
}}

If an individual flexbox item is too large, then it's impossible to
satisfy the condition in step 2 ("keeping the sum of their margin-box
main size smaller than the flexbox's available space")

Presumably we want to handle such cases by giving these items their own
line (which they'll overflow in the main axis, but there's nothing we
can do about that).  Can we add that to the spec?

~Daniel