Plumb net_error alongside ssl_info outside of net/

Various code that is notified about SSL certificate errors uses
MapCertStatusToNetError() to map a cert status from SSLInfo back into
a net error code. However, this is not the intended use of
MapCertStatusToNetError. When there was a net error, we should surface
that directly instead of attempting to reconstruct it with
MapCertStatusToNetError.

As a first step, this CL surfaces the net error outside of net/ in the
URLRequest::Delegate interface. Follow-up CLs will plumb the net error
all the way up to where MapCertStatusToNetError is called.

Bug: 937529
Change-Id: I48084363842c7c300cfdf154c3f4383d2d5cd679
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1570471
Reviewed-by: Ryan Sleevi <rsleevi@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Misha Efimov <mef@chromium.org>
Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Emily Stark <estark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653914}
35 files changed