Require a user gesture for the Contact API

Also provide a series of new tests to cover the implementation,
particularly this requirement.

Bug: 860467
Change-Id: I274e433fadba5228ac5dc0853b5a30354904d43e
Reviewed-on: https://chromium-review.googlesource.com/c/1430014
Commit-Queue: Peter Beverloo <peter@chromium.org>
Reviewed-by: Finnur Thorarinsson <finnur@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625333}
3 files changed