Find native classes with mixins in NativeClassFinder

pkg/compiler/lib/src/native/resolver.dart

Index: pkg/compiler/lib/src/native/resolver.dart
diff --git a/pkg/compiler/lib/src/native/resolver.dart b/pkg/compiler/lib/src/native/resolver.dart
index 0013fade094fb3505ba9a8dfc0b3ddafd88ca7a0..af0dfc4060e3aa4e57a7d0605c43ab247fdf21b3 100644
--- a/pkg/compiler/lib/src/native/resolver.dart
+++ b/pkg/compiler/lib/src/native/resolver.dart
@@ -406,7 +406,9 @@ class BaseNativeClassFinder implements NativeClassFinder {
   /// Returns the name of the super class of [cls] or `null` of [cls] has
   /// no explicit superclass.
   String _findExtendsNameOfClass(ClassEntity cls) {
-    return _elementEnvironment.getSuperClass(cls)?.name;
+    return _elementEnvironment
+        .getSuperClass(cls, skipUnnamedMixinApplications: true)
+        ?.name;
   }
 
   /// Adds all subclasses of [nativeClasses] found in [libraries] to