See example in the URL. setting the margin to auto shouldn't overflow out the top of the flexbox.
This would be a pretty easy bug to fix.
Created attachment 177488 [details] Patch
Comment on attachment 177488 [details] Patch Can you also add asserts in updateAutoMarginsInCrossAxis and updateAutoMarginsInMainAxis that the LayoutUnit passed in is >= 0?
Comment on attachment 177488 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=177488&action=review > LayoutTests/css3/flexbox/flex-flow-auto-margins-no-available-space.html:4 > +<style> > +body { Please use resources/flexbox.css and the styles defined there when possible. This makes the tests runnable in Firefox and makes it easy to add other vendor prefixes to the tests.
Comment on attachment 177488 [details] Patch Committed r136660: <http://trac.webkit.org/changeset/136660>