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

tests/html/js_interop_4_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('JsInterop4Test');
-#import('../../pkg/unittest/unittest.dart');
-#import('../../pkg/unittest/html_config.dart');
-#import('dart:html');
-#import('dart:isolate');
+library JsInterop4Test;
+import '../../pkg/unittest/lib/unittest.dart';
+import '../../pkg/unittest/lib/html_config.dart';
+import 'dart:html';
+import 'dart:isolate';
 
 const testData = const [1, '2', 'true'];
 
 void testIsolateEntry() {
   var fun1 = window.lookupPort('fun1');
   var result = fun1.callSync(testData);
 
   var fun2 = window.lookupPort('fun2');
   fun2.callSync(result);
 }
@@ skipping 35 matching lines @@
       window.setTimeout(done, 0);
     };
 
     var port2 = new ReceivePortSync();
     port2.receive(fun2);
     window.registerPort('fun2', port2.toSendPort());
 
     spawnDomFunction(testIsolateEntry);
   });
 }