The title plugin and scale title now accept lineHeight specified using unitless value (1.4), length ('1.4em' or '12px'), percentage ('200%') or keyword ('normal' === 1.2). The line height parsing has been refactored under the 'Chart.helpers.options' namespace. Also fix incorrect text positioning in the title plugin.
https://developer.mozilla.org/en-US/docs/Web/CSS/line-height