Improve comments on SyncUserSettings

Some of the settings have surprising default values. As a first step,
let's at least document those.

Bug: 884159, 906034
Change-Id: I8ee8ba2d6ffc2886f8bc623062787d6ec8d332ed
Reviewed-on: https://chromium-review.googlesource.com/c/1340301
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609291}
1 file changed