Revert of headless: Allow protocol handler customization (patchset #3 id:40001 of https://codereview.chromium.org/2024973002/ )

Reason for revert:
Doing another review round with net/.

Original issue's description:
> headless: Allow protocol handler customization
>
> Allow headless clients to provide custom protocol handlers. This lets
> the clients override how URL requests are fulfilled for different
> schemes types.
>
> Design doc: https://docs.google.com/document/d/1m4CCZGJWOJdHY5MVwQqY3sT-5kBoz7NqmGvIb6-l3fM/edit#bookmark=id.5bqp8w95liri
>
> BUG=595353
>
> Committed: https://crrev.com/789f9abbbc69e5d485984a9d7b4e3d167054919f
> Cr-Commit-Position: refs/heads/master@{#396884}

TBR=altimin@chromium.org,alexclarke@chromium.org,eseckler@chromium.org,rsleevi@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=595353

Review-Url: https://codereview.chromium.org/2026253002
Cr-Commit-Position: refs/heads/master@{#397093}
6 files changed