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

pkg/webdriver/lib/src/base64decoder.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.
+
+part of webdriver;
+
 /**
  * A simple base64 decoder class, used to decode web browser screenshots
  * returned by WebDriver.
  */
 class Base64Decoder {
 
   static int getVal(String s, pos) {
     int code = s.charCodeAt(pos);
     if (code >= 65 && code < (65+26)) { // 'A'..'Z'
       return code - 65;
@@ skipping 29 matching lines @@
             (getVal(s, pos + 2) << 6) | getVal(s, pos+3);
         pos += 4;
         rtn.add((v >> 16 ) & 0xff);
         rtn.add((v >> 8) & 0xff);
         rtn.add(v & 0xff);
       }
     }
     return rtn;
   }
 }