Get rid of duplication of class node unparsing.

lib/compiler/implementation/dart_backend/emitter.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.
 
 String emitCode(
       Compiler compiler,
       Unparser unparser,
       Map<LibraryElement, String> imports,
       Collection<Element> topLevelElements,
       Map<ClassElement, Collection<Element>> classMembers) {
@@ skipping 11 matching lines @@
       if (!processedVariableLists.contains(variableList)) {
         processedVariableLists.add(variableList);
         unparser.unparse(variableList.parseNode(compiler));
       }
     } else {
       unparser.unparse(element.parseNode(compiler));
     }
   }
 
   void outputClass(ClassElement classElement, Collection<Element> members) {
-    ClassNode classNode = classElement.parseNode(compiler);
-    // classElement.beginToken is 'class', 'interface', or 'abstract'.
-    unparser.addToken(classNode.beginToken);
-    if (classNode.beginToken.stringValue == 'abstract') {
-      unparser.addToken(classNode.beginToken.next);
-    }
-    unparser.unparse(classNode.name);
-    if (classNode.typeParameters !== null) {
-      unparser.unparse(classNode.typeParameters);
-    }
-    if (classNode.extendsKeyword !== null) {
-      unparser.addString(' ');
-      unparser.addToken(classNode.extendsKeyword);
-      unparser.unparse(classNode.superclass);
-    }
-    if (!classNode.interfaces.isEmpty()) {
-      unparser.addString(' ');
-      unparser.unparse(classNode.interfaces);
-    }
-    if (classNode.defaultClause !== null) {
-      unparser.addString(' default ');
-      unparser.unparse(classNode.defaultClause);
-    }
-    unparser.addString('{');
-    members.forEach((element) {
-      // TODO(smok): Filter out default constructors here.
-      outputElement(element);
+    unparser.unparseClassWithBody(classElement.parseNode(compiler), () {
+      members.forEach((element) {
+        // TODO(smok): Filter out default constructors here.
+        outputElement(element);
+      });
     });
-    unparser.addString('}');
   }
 
   imports.forEach((libraryElement, prefix) {
     unparser.addString('#import("${libraryElement.uri}",prefix:"$prefix");');
   });
 
   for (final element in topLevelElements) {
     if (element is ClassElement) {
       outputClass(element, classMembers[element]);
     } else {
       outputElement(element);
     }
   }
 }