Get rid of duplication of class node unparsing.

tests/compiler/dart2js/unparser2_test.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.
 
 #import("../../../lib/compiler/implementation/scanner/scannerlib.dart");
 #import("../../../lib/compiler/implementation/elements/elements.dart"); // only need CompilationUnitElement
 #import("../../../lib/compiler/implementation/tree/tree.dart");
 #import("../../../lib/compiler/implementation/leg.dart"); // only need DiagnosticListener & Script
 
 // This is the number of spaces to trim from the test code.
 // New tests should be indented this amount.
 const int BUILT_IN_TEST_INDENTATION = 6;
 
 main() {
   testClassDef();
   testClass1Field();
   testClass2Fields();
   testClass1Field1Method();
   testClass1Field2Method();
   testClassDefTypeParam();
 }
 
 testClassDef() {
   compareCode('''
       class T{}
       ''', '''
-      class T {
+      class T{
       }
       ''');
 }
 
 testClass1Field() {
   compareCode('''
       class T{var x;}
       ''', '''
-      class T {
+      class T{
         var x;
       }
   ''');
 }
 
 testClass2Fields() {
   compareCode('''
       class T{var x; var y;}
       ''', '''
-      class T {
+      class T{
         var x;
         var y;
       }
   ''');
 }
 
 testClass1Field1Method() {
   compareCode('''
       class T{var x;m(){}}
       ''', '''
-      class T {
+      class T{
         var x;
         m(){}
       }
   ''');
 }
 
 testClass1Field2Method() {
   compareCode('''
       class T{a(){}b(){}}
       ''', '''
-      class T {
+      class T{
         a(){}
         b(){}
       }
   ''');
 }
 
 testClassDefTypeParam() {
   compareCode('''
       class T<X>{}
       ''', '''
-      class T<X> {
+      class T<X>{
       }
       ''');
 }
 
 void compareCode(String original, String expected) {
   String unparsed = doUnparse(cleanUpLiteral(original));
   Expect.equals(cleanUpLiteral(expected), unparsed);
 }
 
 String cleanUpLiteral(String text) {
@@ skipping 37 matching lines @@
   }
   void internalErrorOnElement(Element element, String message) {
     throw message;
   }
   void internalError(String message,
                      [Node node, Token token, Dynamic instruction,
                       Element element]) {
     throw message;
   }
 }