Signed Exchange: Add scripts to generate test data

Bug: 803774
Change-Id: I9c9f9ff1a070b0bcf86312f6a80c56146b9d475b
Reviewed-on: https://chromium-review.googlesource.com/1143095
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Kunihiko Sakamoto <ksakamoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576751}
5 files changed