Enable conditional imports in unparser test.

tests/compiler/dart2js/parser_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.
 
 library parser_helper;
 
 import "package:expect/expect.dart";
 
 import "package:compiler/src/elements/elements.dart";
 import "package:compiler/src/tree/tree.dart";
@@ skipping 84 matching lines @@
 Node parseBodyCode(String text, Function parseMethod,
                    {DiagnosticReporter reporter}) {
   Token tokens = scan(text);
   if (reporter == null) reporter = new LoggerCanceler();
   Uri uri = new Uri(scheme: "source");
   Script script = new Script(uri, uri,new MockFile(text));
   LibraryElement library = new LibraryElementX(script);
   NodeListener listener = new NodeListener(
       new ScannerOptions(canUseNative: true),
       reporter, library.entryCompilationUnit);
-  Parser parser = new Parser(listener);
+  Parser parser = new Parser(listener, enableConditionalDirectives: true);
   Token endToken = parseMethod(parser, tokens);
   assert(endToken.kind == EOF_TOKEN);
   Node node = listener.popNode();
   Expect.isNotNull(node);
   Expect.isTrue(listener.nodes.isEmpty, 'Not empty: ${listener.nodes}');
   return node;
 }
 
 Node parseStatement(String text) =>
   parseBodyCode(text, (parser, tokens) => parser.parseStatement(tokens));
@@ skipping 38 matching lines @@
   reporter.withCurrentElement(unit, () => parser.parseUnit(tokens));
   return unit.localMembers;
 }
 
 NodeList fullParseUnit(String source, {DiagnosticReporter reporter}) {
   return parseBodyCode(
       source,
       (parser, tokens) => parser.parseUnit(tokens),
       reporter: reporter);
 }