NetLog:  Rework ConnectJob logging.

This CL makes it so that the events for nested ConnectJobs are nested
within their parent ConnectJob. This both reduces the number of top
level CONNECT_JOB events in logs, making navigation between top-level
events easier, and makes it easier to see all information related to
establishing a single connection at once.

This didn't used to be possible because there was a socket pool between
nested ConnectJob classes, which introduced a layer of late binding.
However, most of those intermediary socket pools have been removed,
so the events can now be nested directly, for the most part.

Bug: 926899
Change-Id: I7d51ae9e164560fdb0396f21b0ac85370c4b7ae7
Reviewed-on: https://chromium-review.googlesource.com/c/1478259
Reviewed-by: Eric Roman <eroman@chromium.org>
Commit-Queue: Matt Menke <mmenke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634886}
22 files changed