Restructure pkg/unittest and pkg/webdriver to follow the pub conventions.

tests/html/xhr_cross_origin_test.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.
 
-#library('XHRCrossOriginTest');
-#import('../../pkg/unittest/unittest.dart');
-#import('../../pkg/unittest/html_config.dart');
-#import('dart:html');
-#import('dart:json');
+library XHRCrossOriginTest;
+import '../../pkg/unittest/lib/unittest.dart';
+import '../../pkg/unittest/lib/html_config.dart';
+import 'dart:html';
+import 'dart:json';
 
 main() {
   useHtmlConfiguration();
 
   test('XHR Cross-domain', () {
     var url = "http://localhost:9876/tests/html/xhr_cross_origin_data.txt";
     var xhr = new HttpRequest();
     xhr.open('GET', url, true);
     var validate = expectAsync1((data) {
       expect(data, contains('feed'));
@@ skipping 13 matching lines @@
   test('XHR.get Cross-domain', () {
     var url = "http://localhost:9876/tests/html/xhr_cross_origin_data.txt";
     new HttpRequest.get(url, expectAsync1((xhr) {
       var data = JSON.parse(xhr.response);
       expect(data, contains('feed'));
       expect(data['feed'], contains('entry'));
       expect(data, isMap);
     }));
   });
 }