Make unittest follow the new package layout.

tests/html/serialized_script_value_test.dart

 #library('SerializedScriptValueTest');
-#import('../../pkg/unittest/unittest.dart');
-#import('../../pkg/unittest/html_config.dart');
+#import('../../pkg/unittest/lib/unittest.dart');
+#import('../../pkg/unittest/lib/html_config.dart');
 #import('dart:html');
 #import('utils.dart');
 
 serializationTest(name, value) => test(name, () {
       // To check how value is serialized and deserialized, we create a MessageEvent.
     final event = document.$dom_createEvent('MessageEvent');
     event.initMessageEvent('', false, false, value, '', '', window, []);
     verifyGraph(value, event.data);
 });
 
@@ skipping 15 matching lines @@
   serializationTest('cyclic map', cyclicMap);
 
   final simpleList = [ 100, 's'];
   final dagList = [ simpleList, simpleList ];
   final cyclicList = [ dagList ];
   cyclicList.add(cyclicList);
   serializationTest('simple list', simpleList);
   serializationTest('dag list', dagList);
   serializationTest('cyclic list', cyclicList);
 }