[ios] Makes small tweaks to the UIRefresh settings UI.

These tweaks are based on feedback from UX.  See the linked bug
for details.

BUG=863043

Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I159c77e16c567b5b670ca727425253fc8a393ebe
Reviewed-on: https://chromium-review.googlesource.com/1135289
Commit-Queue: Rohit Rao <rohitrao@chromium.org>
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575358}
10 files changed