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

tools/testing/dart/browser_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.
 
 String getHtmlContents(String title,
                        String controllerScript,
                        String dartJsScript,
                        String scriptType,
                        String sourceScript) =>
 """
@@ skipping 29 matching lines @@
   <script type="text/javascript">
     if (navigator.webkitStartDart) navigator.webkitStartDart();
   </script>
   <script type="$scriptType" src="$sourceScript"></script>
 </body>
 </html>
 """;
 
 String wrapDartTestInLibrary(Path test) =>
 """
-#library('libraryWrapper');
-#source('$test');
+library libraryWrapper;
+part '$test';
 """;
 
 String dartTestWrapper(Path dartHome, Path library) =>
 """
-#library('test');
+library test;
 
-#import('${dartHome.append('pkg/unittest/unittest.dart')}', prefix: 'unittest');
-#import('${dartHome.append('pkg/unittest/html_config.dart')}',
-        prefix: 'config');
-
-#import('${library}', prefix: "Test");
+import '${dartHome.append('pkg/unittest/lib/unittest.dart')}' as unittest;
+import '${dartHome.append('pkg/unittest/lib/html_config.dart')}' as config;
+import '${library}' as Test;
 
 main() {
   config.useHtmlConfiguration();
   unittest.group('', Test.main);
 }
 """;