Implement :-moz-native-anonymous support in stylo.

Fixes https://bugzilla.mozilla.org/show_bug.cgi?id=1364591

components/style/gecko/non_ts_pseudo_class_list.rs

@@ -26,8 +26,6 @@
  * Pending pseudo-classes:
  *
  *  :-moz-is-html -> Used only in UA sheets, should be easy to support.
- *  :-moz-native-anonymous -> For devtools, seems easy-ish?
- *  :-moz-bound-element -> Seems unused, should be easy to remove.
  *
  *  :-moz-lwtheme, :-moz-lwtheme-brighttext, :-moz-lwtheme-darktext,
  *  :-moz-window-inactive.
@@ -109,7 +107,7 @@ macro_rules! apply_non_ts_list {
                 ("-moz-first-node", MozFirstNode, firstNode, _, _),
                 ("-moz-last-node", MozLastNode, lastNode, _, _),
                 ("-moz-only-whitespace", MozOnlyWhitespace, mozOnlyWhitespace, _, _),
-
+                ("-moz-native-anonymous", MozNativeAnonymous, mozNativeAnonymous, _, PSEUDO_CLASS_INTERNAL),
             ],
             string: [
                 ("-moz-system-metric", MozSystemMetric, mozSystemMetric, _, PSEUDO_CLASS_INTERNAL),

components/style/gecko/wrapper.rs

@@ -1218,7 +1218,8 @@ impl<'le> ::selectors::Element for GeckoElement<'le> {
                 true
             }
             NonTSPseudoClass::MozTableBorderNonzero |
-            NonTSPseudoClass::MozBrowserFrame => unsafe {
+            NonTSPseudoClass::MozBrowserFrame |
+            NonTSPseudoClass::MozNativeAnonymous => unsafe {
                 Gecko_MatchesElement(pseudo_class.to_gecko_pseudoclasstype().unwrap(), self.0)
             },
             NonTSPseudoClass::MozAny(ref sels) => {