The result of parsing this:
a:after { content: "?" }
is a rule that has a DescendantSelectorImpl with an ElementSelectorImpl as parent (the anchor element) and a PseudoElementSelectorImpl as descendant (for 'after' pseudo element).
Unfortuantelly, the selector is serialized as:
a after
Anonymous
Here's a patch that fixes the issue.
Now fixed in SVN. Thanks for the patch.