When CSS is set in a head tag then it was not being inherited by the child
tags when the CSS specification indicates that the properties are in fact
inherited. This ensures that those properties are inherited and the non
inheritable ones are unchanged.
A test is added to cover the different situations with inheritance and a
fix is done for the QTextDocumentFragment test which was passing despite
having incorrect defaults.
Task-number: QTBUG-28770
Task-number: QTBUG-34153
Change-Id: I55966240845a885852a04ecb82c61926dea9f800
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>
