Revert r22847: some dart2dart tests fail.

tests/compiler/dart2js/parser_helper.dart

Index: tests/compiler/dart2js/parser_helper.dart
===================================================================
--- tests/compiler/dart2js/parser_helper.dart	(revision 22847)
+++ tests/compiler/dart2js/parser_helper.dart	(working copy)
@@ -78,17 +78,10 @@
       : super('<string>', text);
 }
 
-var sourceCounter = 0;
-
 Link<Element> parseUnit(String text, Compiler compiler,
-                        LibraryElement library,
-                        [void registerSource(Uri uri, String source)]) {
+                        LibraryElement library) {
   Token tokens = scan(text);
-  Uri uri =
-      new Uri.fromComponents(scheme: "source", path: '${++sourceCounter}');
-  if (registerSource != null) {
-    registerSource(uri, text);
-  }
+  Uri uri = new Uri.fromComponents(scheme: "source");
   var script = new Script(uri, new MockFile(text));
   var unit = new CompilationUnitElementX(script, library);
   int id = 0;