Bug 867031 - [CustomizeUI] Cannot preload contacts during build time. r=mwu

This reverts commit e6beb3cf80ed83f12e1713799d9fcccca6f3a996.

This patch should merge after gaia part patch: https://github.com/mozilla-b2g/gaia/pull/9777.
Due to gaia part was merged, so this patch can be merged now.

see [Bug 867031](https://bugzilla.mozilla.org/show_bug.cgi?id=867031#c12).