Plumb net error to SSLErrorHandler

A previous CL
(https://chromium-review.googlesource.com/c/chromium/src/+/1570471)
plumbed a net error out of net/ when an SSL error occurs. This CL
plumbs the net error up to SSLErrorHandler, so that a net error
doesn't have to be reconstructed out of a cert status. The end goal is
to make it so that MapCertStatusToNetError is used to synthesize a net
error code when the net stack didn't treat the cert error as an error,
rather than to convert a cert status to an error code even when there
was an actual error.

Bug: 937529
Change-Id: I553061794e4efa7d40e62e0931ed0e7b908ecfd6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1574627
Commit-Queue: Emily Stark <estark@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Ryan Sleevi <rsleevi@chromium.org>
Reviewed-by: Carlos IL <carlosil@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654918}