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As was previously only done for address results, also allow non-address
results to read a TTL from SOA records for NXDOMAIN and NODATA
responses. This allows negative non-address results to be cached (but
only for the non-transient NXDOMAIN and NODATA cases).

For both address and non-address negative response parsing, do not read
any TTLs unless an SOA record is present.  But if an SOA record is
present, still allow using the min TTL between that record and any other
parsed records present (e.g. CNAME records that are still valid to be
present in an NXDOMAIN response).

Fixed: 1121785
Change-Id: I200f45b60c30d89ee53e45fa2cdb70302b617c09
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2446016
Commit-Queue: Eric Orth <ericorth@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813965}