Remove uses of unittest in the HTML tests where possible.

pkg/dev_compiler/test/codegen/lib/html/serialized_script_value_test.dart

-library SerializedScriptValueTest;
-import 'package:unittest/unittest.dart';
-import 'package:unittest/html_config.dart';
 import 'dart:html';
+
+import 'package:expect/minitest.dart';
+
 import 'utils.dart';
 
-serializationTest(name, value) => test(name, () {
+serializationTest(name, value) {
+  test(name, () {
     // To check how value is serialized and deserialized, we create a
     // MessageEvent.
     final event =
         new MessageEvent('', data: value, origin: '', lastEventId: '');
     verifyGraph(value, event.data);
-});
-
+  });
+}
 
 main() {
-  useHtmlConfiguration();
-
   serializationTest('null', null);
   serializationTest('int', 1);
   serializationTest('double', 2.39);
   serializationTest('string', 'hey!');
 
   final simpleMap = {'a': 100, 'b': 's'};
   final dagMap = { 'x': simpleMap, 'y': simpleMap };
   final cyclicMap = { 'b': dagMap };
   cyclicMap['a'] = cyclicMap;
   serializationTest('simple map', simpleMap);
@@ skipping 14 matching lines @@
       ['Indescribable... Indestructible! Nothing can stop it!'],
       'text/plain');
   serializationTest('blob', [blob]);
 
   var canvas = new CanvasElement();
   canvas.width = 100;
   canvas.height = 100;
   var imageData = canvas.context2D.getImageData(0, 0, 1, 1);
   serializationTest('imagedata', [imageData]);
 }