style: Rewrite <input type=number> to avoid an anonymous input.

Instead, subclass nsTextControlFrame. This simplifies the code and avoids
correctness issues.

I kept the localization functionality though it is not spec compliant. But I
filed a bug to remove it in a followup.

Differential Revision: https://phabricator.services.mozilla.com/D57193

components/style/gecko/wrapper.rs

@@ -1869,22 +1869,7 @@ impl<'le> ::selectors::Element for GeckoElement<'le> {
     #[inline]
     fn pseudo_element_originating_element(&self) -> Option<Self> {
         debug_assert!(self.is_pseudo_element());
-        let parent = self.closest_anon_subtree_root_parent()?;
-
-        // FIXME(emilio): Special-case for <input type="number">s
-        // pseudo-elements, which are nested NAC. Probably nsNumberControlFrame
-        // should instead inherit from nsTextControlFrame, and then this could
-        // go away.
-        if let Some(PseudoElement::MozNumberText) = parent.implemented_pseudo_element() {
-            debug_assert_eq!(
-                self.implemented_pseudo_element().unwrap(),
-                PseudoElement::Placeholder,
-                "You added a new pseudo, do you really want this?"
-            );
-            return parent.closest_anon_subtree_root_parent();
-        }
-
-        Some(parent)
+        self.closest_anon_subtree_root_parent()
     }
 
     #[inline]