layout/style/crashtests/437170-1.html triggers ###!!! ASSERTION: should not have pseudo-element data: 'mPseudo || !mStyleContextHolder->HasPseudoElementData()', file layout/style/nsComputedDOMStyle.cpp, line 479
This is, um, rather interesting. The style context in question is the grandchild of a style context with (a) null parent and (b) :-moz-non-element internal pseudo. I guess that's the result of GetStyleContextForContent's handling of document fragments. That handling was introduced a long time ago: http://bonsai.mozilla.org/cvslog.cgi?file=mozilla/extensions/inspector/base/src/inDOMUtils.cpp&rev=1.15 and I think we should instead skip non-element parents.
Created attachment 394156 [details] [diff] [review] patch
Comment on attachment 394156 [details] [diff] [review] patch Simple fix to do less-weird things, to fix an assertion introduced a few days ago.