avm2: Implement flash.system.Capabilities.language

Author: evilpie

core/src/avm2/globals/flash/system/Capabilities.as

@@ -8,14 +8,11 @@ package flash.system {
         public native static function get screenResolutionY():Number;
         public native static function get pixelAspectRatio():Number;
         public native static function get screenDPI():Number;
+        public native static function get language(): String;
         public static function get manufacturer(): String {
             stub_getter("flash.system.Capabilities", "manufacturer");
             return "Adobe Windows"
         }
-        public static function get language(): String {
-            stub_getter("flash.system.Capabilities", "language");
-            return "en"
-        }
         public static function get isDebugger(): Boolean {
             return false
         }

core/src/avm2/globals/flash/system/capabilities.rs

@@ -113,3 +113,17 @@ pub fn get_screen_dpi<'gc>(
     // source: https://tracker.adobe.com/#/view/FP-3949775
     Ok(72.into())
 }
+
+/// Implements `flash.system.Capabilities.language`
+pub fn get_language<'gc>(
+    activation: &mut Activation<'_, 'gc>,
+    _this: Value<'gc>,
+    _args: &[Value<'gc>],
+) -> Result<Value<'gc>, Error<'gc>> {
+    let language = activation
+        .context
+        .system
+        .language
+        .get_language_code(activation.context.player_version);
+    Ok(AvmString::new_utf8(activation.gc(), language).into())
+}