The calculation rounds early and often, which is intentional. Add
unit test to make sure we don't regress.
Fixes static analzyer report about incorrect rounding in
c903a34347776fe3b89785faa35c446d.
Address some outdated comments and documentation. The property
is read only and calculated, so don't imply that it can be changed
from its default value.
Change-Id: If2dbd9890e533dfccda3eae4cbc96db4f1246f4d
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
180f78d126