style: Remove font-size calc() hack to propagate keyword information.

It does not make any sense with min() / max() / clamp. So just forget the
keyword info when calc() is used. This also removes a bit of complex / hacky
code.

Differential Revision: https://phabricator.services.mozilla.com/D60663

components/style/gecko/wrapper.rs

@@ -956,9 +956,8 @@ impl FontMetricsProvider for GeckoFontMetricsProvider {
 
         let (wm, font) = match base_size {
             FontBaseSize::CurrentStyle => (style.writing_mode, style.get_font()),
-            // These are only used for font-size computation, and the first is
-            // really dubious...
-            FontBaseSize::InheritedStyleButStripEmUnits | FontBaseSize::InheritedStyle => {
+            // This is only used for font-size computation.
+            FontBaseSize::InheritedStyle => {
                 (*style.inherited_writing_mode(), style.get_parent_font())
             },
         };