Not sure how long this has been regressed for, less than two weeks ago it changed (haven't been hunting yet). It is a regression from previous nightlies. On a page with an HTML Base element, all relative URLs should be based from the href attribute of the Base element. Currently, @import statements within a 'style' block are left relative to the document.
Added URL with minimal test case. This bug is not present in the release builds of Safari.
Alex, your test case has a link-local hostname as the base URL, so it will not work for anyone other than yourself. Can you please update the test case so that we can look into this bug?
Oh right. Smart move that was. *Slaps forehead* Testcase updated.
Regression occurred between r16681 (Sat Sept 30) and r16691 (Sun Oct 1).
Thanks for the reduction and timeframe Alex.
Probably broke this when fixing bug 11011.
Created attachment 11124 [details] proposed fix
Comment on attachment 11124 [details] proposed fix r=me
Committed revision 17136.
*** Bug 11203 has been marked as a duplicate of this bug. ***