Support compressed messages.json files

This allows extensions to read compressed messages.json.gz files for
l10n if they exist.

For DEPS change:
TBR=cavalcantii@chromium.org

Bug: 1023568
Change-Id: I520a7fd3e05cbe488a5c6623976c4b9dfe4c1e21
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1912830
Commit-Queue: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Ken Rockot <rockot@google.com>
Cr-Commit-Position: refs/heads/master@{#716232}
10 files changed