Update unittest to new package layout.

pkg/intl/test/date_time_format_test_core.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.
 
 /**
  * Tests the DateFormat library in dart. This file contains core tests that
  * are run regardless of where the locale data is found, so it doesn't expect to
  * be run on its own, but rather to be imported and run from another test file.
  */
 
 #library('date_time_format_tests');
 
+// TODO(rnystrom): Use "package:" URL (#4968).
 #import('../date_format.dart');
-#import('../../../pkg/unittest/unittest.dart');
+#import('../../../pkg/unittest/lib/unittest.dart');
 #import('date_time_format_test_data.dart');
 #import('../intl.dart');
 #import('../lib/date_format_internal.dart');
 
 var formatsToTest = const [
   DateFormat.DAY,
   DateFormat.ABBR_WEEKDAY,
   DateFormat.WEEKDAY,
   DateFormat.ABBR_STANDALONE_MONTH,
   DateFormat.STANDALONE_MONTH,
@@ skipping 298 matching lines @@
     var localPrinted = format.format(local);
     var parsed = format.parse(localPrinted);
     var parsedUTC = format.parseUTC(format.format(utc));
     var parsedOffset = parsedUTC.millisecondsSinceEpoch
         - parsed.millisecondsSinceEpoch;
     expect(parsedOffset, equals(offset));
     expect(utc.hour, equals(parsedUTC.hour));
     expect(local.hour, equals(parsed.hour));
     });
 }