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Generally just applies the mapping to the input HostPortPair and passes
on to the wrapped implementation. Some special handling for when the
input is mapped to an error.

Bug: 821021
Change-Id: I0d108976e363993ebb36b8081948ef410894fa47
Reviewed-on: https://chromium-review.googlesource.com/1156856Reviewed-by: Matt Menke <mmenke@chromium.org>
Commit-Queue: Eric Orth <ericorth@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579587}