Ensure CT is only enforced for Official Chrome Builds

This changes Certificate Transparency to only be enforced
for official Chrome builds, disabling Certificate Transparency
for Chromium, as well as any Chromium-derived builds that are
not using the //src/content layer.

The motivations are captured within
//net/docs/certificate-transparency.md , and in particular,
"Supporting Certificate Transparency for Embedders". This
change ensures that Chromium-derived browsers (i.e. those that
take and customize //chrome rather than using //content), as
well as distro-customized Chromium distributions, do not
encounter connection errors due to relying upon an out-of-date
Certificate Transparency Log list.

This is temporary; future work will seek to enable a clearer
communication about the date at which the log list was based
on, as well as the ability to update out of band, which will
facilitate both Chromium distributors and those Chromium-derived
browsers that support the component updater.


Bug: 973378
Change-Id: Ia72c88320ffba7582efdf4bcaf062174cca4ad16
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1774327
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Commit-Queue: Ryan Sleevi <rsleevi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691802}
12 files changed