Add tests for problem with newline encoding in multiline strings.

tests/language/multiline_newline_lf.dart

 // Copyright (c) 2015, 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.
 
-// Deferred library loaded by deferred_split_test.dart
+library multiline_newline_lf;
 
-import 'deferred_split_lib1.dart';
+const constantMultilineString = """
+a
+b
+""";
 
-createA() => new A();
+var nonConstantMultilineString = """
+a
+b
+""";