Update dart2js unit tests to new library API.

dart/tests/compiler/dart2js/compiler_helper.dart

Index: dart/tests/compiler/dart2js/compiler_helper.dart
diff --git a/dart/tests/compiler/dart2js/compiler_helper.dart b/dart/tests/compiler/dart2js/compiler_helper.dart
index 2bc5a08e06db2c010194393bc7ba2fdd509113d2..ebebfa663e094f4aced4a5ec723432491b6f26f1 100644
--- a/dart/tests/compiler/dart2js/compiler_helper.dart
+++ b/dart/tests/compiler/dart2js/compiler_helper.dart
@@ -82,11 +82,12 @@ String getNumberTypeCheck(String variable) {
 }
 
 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) {