In QUIC, derive IETF long header type from encryption level. Protected by ENABLED gfe2_reloadable_flag_quic_encryption_driven_header_type.

Merge internal change: 233120191

R=rch@chromium.org

Change-Id: Ie9c40630799d46e00289df31f6da9620a8f4a9e3
Reviewed-on: https://chromium-review.googlesource.com/c/1473131
Reviewed-by: Ryan Hamilton <rch@chromium.org>
Commit-Queue: Fan Yang <fayang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632222}
7 files changed