Socket Pools Refactor 25:  Merge the HTTP proxy pool and its children.

The HTTP proxy pool used to sit on top of an SSL pool and a TCP pool.
This CL removes them and has HTTP proxy ConnectJobs directly create
lower layer connections.

This is part of an effort to flatten the socket pools.
https://docs.google.com/document/d/1g0EA4iDqaDhNXA_mq-YK3SlSX-xRkoKvZetAQqdRrxM/edit

Change-Id: Ie6b059732696e339c9ae5a60673821c03233516f
Reviewed-on: https://chromium-review.googlesource.com/c/1453807
Commit-Queue: Matt Menke <mmenke@chromium.org>
Reviewed-by: Bence Béky <bnc@chromium.org>
Reviewed-by: Eric Roman <eroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631905}
15 files changed