Use "overflow-[x/y]: auto;" instead of "overflow-[x/y]: scroll" in Conpherence
Summary: scroll always shows the scroll bar, auto shows it only if scrolling needs to happen. Fixes some weirdness in the blank/empty states in Safari, at least.
Test Plan: Looked at Conpherence in Safari.
Reviewers: btrahan, chad
Reviewed By: chad
CC: aran
Differential Revision: https://secure.phabricator.com/D4635