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.
Per css-ui-4, setting `appearance: none` is supposed to suppress the
creation of a native-looking widget for stuff like checkboxes, radio
buttons, etc.
This patch implements this behavior by simply falling back to creating
a layout node based on the CSS `display` property in such cases.
This fixes an issue on the hey.com imbox page where we were rendering
checkboxes on top of sender profile photos.
