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

tests/html/xmlelement_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('XMLElementTest');
-#import('../../pkg/unittest/unittest.dart');
-#import('../../pkg/unittest/html_config.dart');
-#import('dart:html');
+library XMLElementTest;
+import '../../pkg/unittest/lib/unittest.dart';
+import '../../pkg/unittest/lib/html_config.dart';
+import 'dart:html';
 
 main() {
   useHtmlConfiguration();
 
   var isXMLElement = predicate((x) => x is XMLElement, 'is an XMLElement');
 
   XMLElement makeElement() => new XMLElement.xml("<xml><foo/><bar/></xml>");
 
   makeElementWithParent() {
     final parent = new XMLElement.xml(
@@ skipping 553 matching lines @@
     makeElement().rect.then(
       expectAsync1(ElementRect rect) {
         expectEmptyRect(rect.client);
         expectEmptyRect(rect.offset);
         expectEmptyRect(rect.scroll);
         expectEmptyRect(rect.bounding);
         expect(rect.clientRects.isEmpty, isTrue);
       }));
   });
 }