Broken off from bug 14868.
Created attachment 16602 [details] Patch
Comment on attachment 16602 [details] Patch r=me
Created attachment 16603 [details] Patch2 Slightly updated test case and ChangeLog to reflect the full scope of this change.
Comment on attachment 16603 [details] Patch2 r=me
Created attachment 16604 [details] Patch3 This one includes the updated layout test results, too. (I guess I'll r+ it myself.)
Created attachment 16605 [details] Patch4 One more time with the right layout test results. This time for sure!
Committed revision 26621.