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

tests/json/json_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.
 
-#library('json_tests');
-
-#import('dart:json');
-#import('dart:html');
-#import('../../pkg/unittest/unittest.dart');
-#import('../../pkg/unittest/html_config.dart');
+library json_tests;
+import 'dart:json';
+import 'dart:html';
+import '../../pkg/unittest/lib/unittest.dart';
+import '../../pkg/unittest/lib/html_config.dart';
 
 main() {
   useHtmlConfiguration();
   test('Parse', () {
     // Scalars.
     expect(JSON.parse(' 5 '), equals(5));
     expect(JSON.parse(' -42 '), equals(-42));
     expect(JSON.parse(' 3e0 '), equals(3));
     expect(JSON.parse(' 3.14 '), equals(3.14));
     expect(JSON.parse('true '), isTrue);
@@ skipping 132 matching lines @@
 
 /**
  * Checks that the argument can be converted to a JSON string and
  * back, and produce something equivalent to the argument.
  */
 validateRoundTrip(expected) {
   expect(JSON.parse(JSON.stringify(expected)), equals(expected));
 }