Update dart2js unit tests to dart_parser and dart_scanner.

tests/compiler/dart2js/unparser2_test.dart

Index: tests/compiler/dart2js/unparser2_test.dart
diff --git a/tests/compiler/dart2js/unparser2_test.dart b/tests/compiler/dart2js/unparser2_test.dart
index 820fab7ec91a28cae1d13ce3e2f32398bfd1fc4f..159b417edae8c3fcd54b94efe6ea0a0370332248 100644
--- a/tests/compiler/dart2js/unparser2_test.dart
+++ b/tests/compiler/dart2js/unparser2_test.dart
@@ -5,9 +5,8 @@
 import "package:expect/expect.dart";
 import "package:compiler/src/parser/element_listener.dart";
 import "package:compiler/src/parser/node_listener.dart";
-import "package:compiler/src/parser/parser.dart";
-import "package:compiler/src/scanner/string_scanner.dart";
-import "package:compiler/src/tokens/token.dart";
+import "package:dart_parser/dart_parser.dart";
+import "package:dart_scanner/dart_scanner.dart";
 import "package:compiler/src/tree/tree.dart";
 
 import "package:compiler/src/diagnostics/diagnostic_listener.dart";
@@ -17,8 +16,6 @@ import "package:compiler/src/elements/modelx.dart"
     show CompilationUnitElementX, LibraryElementX;
 import "package:compiler/src/script.dart";
 
-import "options_helper.dart";
-
 main() {
   testClassDef();
   testClass1Field();
@@ -89,7 +86,7 @@ String doUnparse(String source) {
   Script script = new Script(null, null, null);
   LibraryElement lib = new LibraryElementX(script);
   CompilationUnitElement element = new CompilationUnitElementX(script, lib);
-  StringScanner scanner = new StringScanner.fromString(source);
+  StringScanner scanner = new StringScanner(source);
   Token beginToken = scanner.tokenize();
   NodeListener listener =
       new NodeListener(const ScannerOptions(), diagnosticListener, element);