Implement part-of directive.

dart/tests/language/part_test.dart

Index: dart/tests/language/part_test.dart
diff --git a/dart/tests/language/string_escape1_negative_test.dart b/dart/tests/language/part_test.dart
similarity index 71%
copy from dart/tests/language/string_escape1_negative_test.dart
copy to dart/tests/language/part_test.dart
index b9816b1206e18d93470679b9f75c531bc0bebca0..740e17c6ad6aac435d841412e1d7f3c4a198e82f 100644
--- a/dart/tests/language/string_escape1_negative_test.dart
+++ b/dart/tests/language/part_test.dart
@@ -2,10 +2,12 @@
 // 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.
 
-// Test that newlines cannot be escaped in library tags.
+// @static-clean
 
-#library('foo\
-');
+library org.dartlang.test.part_test;
+
+part "part_part.dart";
 
 main() {
+  print(foo);
 }