feat(UI): Use Intl.DisplayNames to show the language name (shaka-proj…

…ect#5365)

ui/language_utils.js

@@ -193,6 +193,21 @@ shaka.ui.LanguageUtils = class {
     // Extract the base language from the locale as a fallback step.
     const language = shaka.util.LanguageUtils.getBase(locale);
 
+    // If Intl.DisplayNames is supported we prefer it, because the list of
+    // languages is up to date.
+    if (window.Intl && 'DisplayNames' in Intl) {
+      try {
+        if (Intl.DisplayNames.supportedLocalesOf([locale]).length) {
+          const languageNames =
+              new Intl.DisplayNames([locale], {type: 'language'});
+          const language = languageNames.of(locale);
+          return language.charAt(0).toUpperCase() + language.slice(1);
+        }
+      } catch (e) {
+        // Ignore errors and try the fallback
+      }
+    }
+
     // First try to resolve the full language name.
     // If that fails, try the base.
     // Finally, report "unknown".