Revert "Fix casts and type assertions on mixins used in native classes."

sdk/lib/_internal/compiler/implementation/compiler.dart

Index: sdk/lib/_internal/compiler/implementation/compiler.dart
diff --git a/sdk/lib/_internal/compiler/implementation/compiler.dart b/sdk/lib/_internal/compiler/implementation/compiler.dart
index 5f40a5870f5f83dee1bb03988c531fdfe98433a5..64d3b69ef0a5a66c0a5d0094ef1a2c3723529b3f 100644
--- a/sdk/lib/_internal/compiler/implementation/compiler.dart
+++ b/sdk/lib/_internal/compiler/implementation/compiler.dart
@@ -164,9 +164,7 @@ abstract class Backend {
                        TreeElements elements) {}
 
   /// Register an as check to the backend.
-  void registerAsCheck(DartType type,
-                       Enqueuer enqueuer,
-                       TreeElements elements) {}
+  void registerAsCheck(DartType type, TreeElements elements) {}
 
   /// Register that the application may throw a [NoSuchMethodError].
   void registerThrowNoSuchMethod(TreeElements elements) {}