fixes Bug 764756, fixes Bug 878414, fixes Bug 885443 - skiplist changes

roll up of three skiplist changes from: 

https://bugzilla.mozilla.org/show_bug.cgi?id=764756
https://bugzilla.mozilla.org/show_bug.cgi?id=878414
https://bugzilla.mozilla.org/show_bug.cgi?id=885443