BREAKING CHANGE:
`$item-ios-divider-bg` is now `$item-ios-divider-background`
`$item-ios-sliding-content-bg` is now
`$item-ios-sliding-content-background`
`$item-md-divider-bg` is now `$item-md-divider-background`
`$item-md-sliding-content-bg` is now
`$item-md-sliding-content-background`
`$item-wp-divider-bg` is now `$item-wp-divider-background`
`$item-wp-sliding-content-bg` is now
`$item-wp-sliding-content-background`
references #5651
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