fix #29544, mixins to a class with named 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 7d48033577925893ea6a616c65b1ead567126a62..ca3f810efefff793e7aeace8997be7194b3755f9 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
@@ -33,7 +33,7 @@ mixin(base, @rest mixins) => JS(
   for (let m of $mixins) {
     $copyProperties(Mixin.prototype, m.prototype);
   }
-  // Initializer method: run mixin initializers, then the base.
+  // Initializer methods: run mixin initializers, then the base.
   Mixin.prototype.new = function(...args) {
     // Run mixin initializers. They cannot have arguments.
     // Run them backwards so most-derived mixin is initialized first.
@@ -43,6 +43,20 @@ mixin(base, @rest mixins) => JS(
     // Run base initializer.
     $base.prototype.new.apply(this, args);
   };
+  let namedCtors = ${safeGetOwnProperty(base, _namedConstructors)};
+  if ($base[$_namedConstructors] != null) {
+    for (let namedCtor of $base[$_namedConstructors]) {
+      Mixin.prototype[namedCtor] = function(...args) {
+        // 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].prototype.new.call(this);
+        }
+        // Run base initializer.
+        $base.prototype[namedCtor].apply(this, args);
+      };
+    }
+  }
 
   // Set the signature of the Mixin class to be the composition
   // of the signatures of the mixins.
@@ -424,13 +438,18 @@ defineNamedConstructor(clazz, name) => JS(
   let proto = $clazz.prototype;
   let initMethod = proto[$name];
   let ctor = function(...args) { initMethod.apply(this, args); };
-  ctor[$isNamedConstructor] = true;
   ctor.prototype = proto;
   // Use defineProperty so we don't hit a property defined on Function,
   // like `caller` and `arguments`.
   $defineProperty($clazz, $name, { value: ctor, configurable: true });
+
+  let namedCtors = ${safeGetOwnProperty(clazz, _namedConstructors)};
+  if (namedCtors == null) $clazz[$_namedConstructors] = namedCtors = [];
+  namedCtors.push($name);
 })()''');
 
+final _namedConstructors = JS('', 'Symbol("_namedConstructors")');
+
 final _extensionType = JS('', 'Symbol("extensionType")');
 
 getExtensionType(obj) => JS('', '#[#]', obj, _extensionType);