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Fairly basic and the connection must be manually torn down for now, but
allows requesting an interface implemention from the JS side.

Bug: 883496
Change-Id: I8367fd50097403ee2f9911657afbabdd8d461a41
Reviewed-on: https://chromium-review.googlesource.com/c/1324929
Commit-Queue: Scott Graham <scottmg@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606663}