In CSS3 Flexbox, it's handy to be able to allow a flex item to shrink below its flex-basis, down to its min-content size, and no smaller. The flexbox spec originally supported this use-case via the "auto" keyword for min-height & min-width, but now that keyword has been removed, partly because the generic "min-content" keyword from CSS3 Intrinsic Sizing can hypothetically be used in its place. However, we don't yet support "min-content" as a height value (for 'height' and 'min-height'). Filing this bug to track adding support for this, at least in min-height. The work may happen in another bug, but I'm filing this at least as a placeholder bug. (At least one flexbox reftest depends on this behavior, now that "auto" is going away, and I'd like to just mark that test as failing for the time being, with a comment pointing to this bug.)