GitLab

Add enums to the browser protocol in prep for the devtools frontend
work.

This CL also updates the network_handler to insert the new values.

Bug: 1136839
Change-Id: I23f9d47bffde3dce3917d41d5c01070646b3d366
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2461595Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Steven Bingler <bingler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816666}