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.
Before this change, we only considering `grid-auto-flow` to determine
whether a row or column should be added when there was not enough space
in the implicit grid to fit the next unplaced item.
Now, we also choose the direction in which the "auto placement cursor"
is moved, based on the auto flow property.
