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.
If a block with inline children ends with a line break clearing any
floats, we not only need to take the introduced clearance into account
for the next line box, but the containing block needs to set the correct
height as well.
Since the spec calls for using the last line box' bottom as the resolved
height (if treated as auto), we now correctly apply the clearance to the
previous line box' bottom coordinate.
Fixes#4058.
