Revert "R4: Remove custom scrollbar use in Javascript"

This reverts commit 85d311ac62cf4f962dd779c2ee652bf0601bfa90.
Revert "R4: Add native browser scrollbars with CSS"

This reverts commit 3f7129bd9370e41cd341bda9aaa310a3b5db98e9.
R4; Begin work on dynamic scroller