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.
Previously the input element was displayed with value 0, when no value
was set in the HTML. Now it uses `value_sanitization_algorithm()`, which
will calculate the default value.
In `value_sanitization_algorithm()` there was a logical mistake/typo.
The comment from the spec says "unless the maximum is less than the
minimum".
The added layout test would fail without the code changes.
Fixes#520
