Move unittest from lib to pkg.

tests/html/measurement_test.dart

 // Copyright (c) 2011, 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('MeasurementTest');
-#import('../../lib/unittest/unittest.dart');
-#import('../../lib/unittest/html_config.dart');
+#import('../../pkg/unittest/unittest.dart');
+#import('../../pkg/unittest/html_config.dart');
 #import('dart:html');
 
 main() {
   useHtmlConfiguration();
 
   test('measurement is async but before setTimout 0', () {
     final element = document.body;
     bool timeout0 = false;
     bool fnComplete = false;
     bool animationFrame = false;
@@ skipping 20 matching lines @@
     final element = document.body;
     rect = element.rect;
     computedStyle = element.computedStyle;
     expect(rect.isComplete, isFalse);
     expect(computedStyle.isComplete, isFalse);
   });
 
   // TODO(jacobr): add more tests that the results return by measurement
   // functions are correct.
 }