Refactor program traversing logic.

tests/compiler/dart2js/unparser_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('dart:uri');
 #import('parser_helper.dart');
 #import("../../../lib/compiler/compiler.dart");
 #import("../../../lib/compiler/implementation/tree/tree.dart");
 
 testUnparse(String statement) {
@@ skipping 170 matching lines @@
   testDart2Dart('main(){final var x,y; final String s;}');
   testDart2Dart('foo(f,g){}main(){foo(1,2);}');
   testDart2Dart('foo(f(arg)){}main(){foo(main);}');
   // A couple of static/finals inside a class.
   testDart2Dart('main(){A.a; A.b;}class A{static final String a="5";'
       'static final String b="4";}');
   // Class member of typedef-ed function type.
   // Maybe typedef should be included in the result too, but it
   // works fine without it.
   testDart2Dart(
-    'main(){new A((arg){});}typedef void foofunc(arg);'
+    'typedef void foofunc(arg);main(){new A((arg){});}'
     'class A{A(foofunc this.handler);final foofunc handler;}');
 }
 
 testGetSet() {
   // Top-level get/set.
   testDart2Dart('set foo(arg){}get foo(){return 5;}main(){foo; foo=5;}');
   // Field get/set.
   testDart2Dart('main(){var a=new A(); a.foo; a.foo=5;}'
       'class A{set foo(a){}get foo(){return 5;}}');
   // Typed get/set.
@@ skipping 236 matching lines @@
   testFactoryConstructor();
   testAbstractClass();
   testConflictSendsRename();
   testNoConflictSendsRename();
   testConflictLibraryClassRename();
   testDefaultClassWithArgs();
   testClassExtendsWithArgs();
   testStaticInvocation();
   testLibraryGetSet();
 }