Revert "Merge pull request #11916 from reubenmorais/contacts-webidl"

This reverts commit 3286df632d9a1c47b667e888be2a98838d972c17, reversing
changes made to fb758390a5e926b8582816a6cce80804dd802b66.

This is breaking two Gaia-UI-tests:
https://travis-ci.org/mozilla-b2g/gaia/jobs/11945544