Get rid of use of dart:html in unittestlib.

client/testing/unittest/unittest.dart

Index: client/testing/unittest/unittest.dart
diff --git a/client/testing/unittest/unittest.dart b/client/testing/unittest/unittest.dart
index 09f0cda29e6a9e2d8b7b5d656235f029897c7e57..045bbccfcd62b81d8c4db21effad8f3713559fbd 100644
--- a/client/testing/unittest/unittest.dart
+++ b/client/testing/unittest/unittest.dart
@@ -2,15 +2,11 @@
 // 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.
 
-// Version of unittest library that uses the html library versions of 'window'
-// and 'document'.
-
-// TODO: When it is possible to use both dom and html in the same program
-// (i.e. using namespaces to distinguish the two global window() getters),
-// remove one of the versions.
-
+/**
+ * A simple unit test library.
+ */
 #library("unittest");
 
-#import("dart:html");
+#import("dart:dom");
 
 #source("unittestsuite.dart");