Handle modifiers (abstract) on class nodes.

lib/compiler/implementation/tree/nodes.dart

 // Copyright (c) 2012, 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.
 
 abstract class Visitor<R> {
   R visitBlock(Block node);
   R visitBreakStatement(BreakStatement node);
   R visitCascade(Cascade node);
   R visitCascadeReceiver(CascadeReceiver node);
   R visitCaseMatch(CaseMatch node);
@@ skipping 154 matching lines @@
   Typedef asTypedef() => null;
   TypeVariable asTypeVariable() => null;
   VariableDefinitions asVariableDefinitions() => null;
   While asWhile() => null;
 
   bool isValidBreakTarget() => false;
   bool isValidContinueTarget() => false;
 }
 
 class ClassNode extends Node {
+  final Modifiers modifiers;
   final Identifier name;
   final TypeAnnotation superclass;
   final NodeList interfaces;
   final NodeList typeParameters;
   final NodeList body;
 
   // TODO(ahe, karlklose): the default keyword is not recorded.
   final TypeAnnotation defaultClause;
 
   final Token beginToken;
   final Token extendsKeyword;
   final Token endToken;
 
-  ClassNode(this.name, this.typeParameters, this.superclass, this.interfaces,
-            this.defaultClause, this.beginToken, this.extendsKeyword,
-            this.body, this.endToken);
+  ClassNode(this.modifiers, this.name, this.typeParameters, this.superclass,
+            this.interfaces, this.defaultClause, this.beginToken,
+            this.extendsKeyword, this.body, this.endToken);
 
   ClassNode asClassNode() => this;
 
   accept(Visitor visitor) => visitor.visitClassNode(this);
 
   visitChildren(Visitor visitor) {
     if (name !== null) name.accept(visitor);
     if (typeParameters !== null) typeParameters.accept(visitor);
     if (superclass !== null) superclass.accept(visitor);
     if (interfaces !== null) interfaces.accept(visitor);
@@ skipping 1692 matching lines @@
  * argument).
  *
  * TODO(ahe): This method is controversial, the team needs to discuss
  * if top-level methods are acceptable and what naming conventions to
  * use.
  */
 initializerDo(Node node, f(Node node)) {
   SendSet send = node.asSendSet();
   if (send !== null) return f(send.arguments.head);
 }