I thought Length's default value is fixed 0, but actually it's auto-0. For the optional arguments of inset shape, we need to use fixed-0, so I updated the code and the tests to use that explicitly.
Created attachment 218484 [details] Patch
Comment on attachment 218484 [details] Patch r=me
Comment on attachment 218484 [details] Patch Clearing flags on attachment: 218484 Committed r160176: <http://trac.webkit.org/changeset/160176>
All reviewed patches have been landed. Closing bug.