Update dart2js unit tests to new library API.

dart/tests/compiler/dart2js/compiler_helper.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.
 // Test constant folding.
 
 library compiler_helper;
 
 import "dart:uri";
 
 import "../../../sdk/lib/_internal/compiler/implementation/elements/elements.dart"
@@ skipping 64 matching lines @@
 
 String getIntTypeCheck(String variable) {
   return "\\($variable ?!== ?\\($variable ?\\| ?0\\)\\)";
 }
 
 String getNumberTypeCheck(String variable) {
   return """\\(typeof $variable ?!== ?"number"\\)""";
 }
 
 bool checkNumberOfMatches(Iterator it, int nb) {
+  bool hasNext = it.moveNext();
   for (int i = 0; i < nb; i++) {
-    Expect.isTrue(it.hasNext, "Found less than $nb matches");
-    it.next();
+    Expect.isTrue(hasNext, "Found less than $nb matches");
+    hasNext = it.moveNext();
   }
-  Expect.isFalse(it.hasNext, "Found more than $nb matches");
+  Expect.isFalse(hasNext, "Found more than $nb matches");
 }
 
 void compileAndMatch(String code, String entry, RegExp regexp) {
   String generated = compile(code, entry: entry);
   Expect.isTrue(regexp.hasMatch(generated),
                 '"$generated" does not match /$regexp/');
 }
 
 void compileAndDoNotMatch(String code, String entry, RegExp regexp) {
   String generated = compile(code, entry: entry);
@@ skipping 19 matching lines @@
   final xRe = new RegExp('\\bx\\b');
   regexp = regexp.replaceAll(xRe, '(?:$anyIdentifier)');
   final spaceRe = new RegExp('\\s+');
   regexp = regexp.replaceAll(spaceRe, '(?:\\s*)');
   if (shouldMatch) {
     Expect.isTrue(new RegExp(regexp).hasMatch(generated));
   } else {
     Expect.isFalse(new RegExp(regexp).hasMatch(generated));
   }
 }