Convert away from method method JSONReader::ReadDeprecated

Replace usage to instead use JSONReader::Read that returns a
base::Optional<base::Value> and convert surrounding code to
the new base::Value API.

Bug: 925165
Change-Id: Ida5525eedca3d679be6c042023bdf2f536576277
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1518514
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#640349}
8 files changed