Changeset 38948 for trunk/src/wp-includes/customize/class-wp-customize-background-position-control.php

Customize: Improve custom background properties UI.

Introduces new control for managing the background position. Adds control for setting the background-size.

Props cdog, celloexpressions, grapplerulrich, MikeHansenMe, FolioVision, afercia, helen, melchoyce, karmatosed, westonruter, Kelderic, sebastian.pisula.
Fixes #22058.