This also fixes a potential bug where ReadHttpJsonResponse could
improperly return None if the server had a completely empty reply.
ReadHttpJsonResponse will now return an empty dictionary in this
case (which is the assumption that most of the callsites are
making).
R=yiwzhang@google.com
Bug: 336351842
Change-Id: I0aa88e233563a0685b6c0f32ea77ad3e094b9cbc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5585184
Reviewed-by: Yiwei Zhang <yiwzhang@google.com>
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>
Auto-Submit: Robbie Iannucci <iannucci@chromium.org>