Sync caption settings via ARC++

This CL adds the synchronization of caption settings via ARC++. Of the
7 caption settings, the following are synced: text font, text color,
text opacity, text shadow, background color, and background opacity.
The text font preference is not synced because it does not map to an
Android setting. The closest setting on the Android side is typeface,
which is an enum with the values DEFAULT, MONOSPACE, SANS_SERIF, and SERIF.
Android has additional caption settings such as caption window color which
are not synced because they do not exist in Chrome

Corresponding Android-side CL:

Bug: 985161
Test: Manually tested the syncing of preferences
Change-Id: Ife8166075a6e2e355960b60a8b292dd23fa6a588
Reviewed-by: Sara Kato <>
Reviewed-by: Mustafa Emre Acer <>
Reviewed-by: Colin Blundell <>
Commit-Queue: Evan Liu <>
Cr-Commit-Position: refs/heads/master@{#685703}
11 files changed