nsScrollbarFrame::CreateAnonymousContent() would create the children
markup originally created by XBL. The attributes updated by XBL attribute
inheritance is updated by nsScrollbarFrame::UpdateChildrenAttributeValue().
This removes the XBL part of the scrollbar implementation.
MozReview-Commit-ID: FWi3HR2qkwF
--HG--
extra : rebase_source : c0b1b2ddbccb1d8e9d523db91a5b81fbcfa328e9
Bug 873010 - Artifacts around small overlay scrollbars in select boxes, r=mstange
--HG--
extra : rebase_source : 002fdce7f49d852e567438481609be58dd76bcc4