Browsers such as Chrome and Firefox apply an arbitrary scale to the
current font size if `normal` is used for `line-height`. Firefox uses
1.2 while Chrome uses 1.15. Let's go with the latter for now, it's
relatively easy to change if we ever want to go back on that decision.
This also requires updating the expectations for a lot of layout tests.
The upside of this is that it's a bit easier to compare our layout
results to other browsers', especially Chrome.
Containing block for abspos grid items depends on their grid placement:
- if element has definite grid position, then corresponding grid area
should be used as a containing block
- if element does not have definite grid position, then padding edge of
grid container should be used as a containing block
So offset should be adjusted for paddings only for boxes without
definite grid position.
