dart2js: Support mixins in the new emitter.

pkg/compiler/lib/src/js_emitter/model.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.new_js_emitter.model;
 
 import '../js/js.dart' as js show Expression;
 import '../constants/values.dart' show ConstantValue;
 
 class Program {
@@ skipping 114 matching lines @@
   final bool isFinal;
   final bool isLazy;
 
   StaticField(this.name, this.holder, this.code,
               this.isFinal, this.isLazy);
 }
 
 class Class {
   final String name;
   final Holder holder;
-  Class superclass;
+  Class _superclass;
   final List<Method> methods;
   final List<InstanceField> fields;
   final bool onlyForRti;
+  final bool isDirectlyInstantiated;
 
   /// Whether the class must be evaluated eagerly.
   bool isEager = false;
 
   Class(this.name, this.holder, this.methods, this.fields,
-        { this.onlyForRti }) {
+        {this.onlyForRti,
+         this.isDirectlyInstantiated}) {
     assert(onlyForRti != null);
+    assert(isDirectlyInstantiated != null);
   }
 
+  bool get isMixinApplication => false;
+  Class get superclass => _superclass;
+
   void setSuperclass(Class superclass) {
-    this.superclass = superclass;
+    _superclass = superclass;
   }
 
   String get superclassName
       => (superclass == null) ? "" : superclass.name;
   int get superclassHolderIndex
       => (superclass == null) ? 0 : superclass.holder.index;
 }
 
+class MixinApplication extends Class {
+  Class _mixinClass;
+
+  MixinApplication(String name, Holder holder,
+                   {bool onlyForRti,
+                    bool isDirectlyInstantiated})
+      : super(name, holder, const <Method>[], const <InstanceField>[],
+              onlyForRti: onlyForRti,
+              isDirectlyInstantiated: isDirectlyInstantiated);
+
+  bool get isMixinApplication => true;
+  Class get mixinClass => _mixinClass;
+
+  void setMixinClass(Class mixinClass) {
+    _mixinClass = mixinClass;
+  }
+}
+
 class InstanceField {
   final String name;
 
   /// 00: Does not need any getter.
   /// 01:  function() { return this.field; }
   /// 10:  function(receiver) { return receiver.field; }
   /// 11:  function(receiver) { return this.field; }
   final int getterFlags;
 
   /// 00: Does not need any setter.
@@ skipping 13 matching lines @@
   final String name;
   final js.Expression code;
   Method(this.name, this.code);
 }
 
 class StaticMethod extends Method {
   final Holder holder;
   StaticMethod(String name, this.holder, js.Expression code)
       : super(name, code);
 }