fix mixins with factory constructors

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/classes.dart

Index: pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/classes.dart
diff --git a/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/classes.dart b/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/classes.dart
index 6a2e36ad82d200cb4f4952c01268327022b4ade8..6d3de87bb788021113fc1f0acf0a82ba788f26a3 100644
--- a/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/classes.dart
+++ b/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/classes.dart
@@ -46,7 +46,8 @@ mixin(base, @rest mixins) => JS(
         // Run mixin initializers. They cannot have arguments.
         // Run them backwards so most-derived mixin is initialized first.
         for (let i = $mixins.length - 1; i >= 0; i--) {
-          $mixins[i].new.call(this);
+          let m = $mixins[i];
+          (m[$mixinNew] || m.new).call(this);
         }
         // Run base initializer.
         $base[memberName].apply(this, args);
@@ -109,6 +110,8 @@ final _typeArguments = JS('', 'Symbol("typeArguments")');
 
 final _originalDeclaration = JS('', 'Symbol("originalDeclaration")');
 
+final mixinNew = JS('', 'Symbol("dart.mixinNew")');
+
 /// Wrap a generic class builder function with future flattening.
 flattenFutures(builder) => JS(
     '',