CSS style such as "line-height: 1.5;" should be used as a multiplier,
but Qt uses it as percentage which makes line spacing way too small. To
workaround this, convert it to percent and use as
QTextBlockFormat::ProportionalHeight instead.
[ChangeLog][QtGui][Important Behvior Changes] Changed CSS line-height
property with multiplier to follow CSS spec
Task-number: QTBUG-56848
Task-number: QTCREATORBUG-17683
Change-Id: Icc98f7c0d4d07542a220702c287f23fa450ef875
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>
ecf440d89d