Modified FindFrameWithContent() to skip over sibling :before pseudo frames when
looking for the primary frame for non-splittable-element aContent.
r=dbaron@fas.harvard.edusr=waterson@netscape.com
git-svn-id: svn://10.0.0.236/trunk@108697 18797224-902f-48f8-a5cc-f745e15eee43