Moved most of html lib generating scripts into tools.

tools/dom/templates/html/dart2js/impl_URL.darttemplate

 // 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.
 
 part of html;
 
 /// @domName $DOMNAME
 class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 
   static String createObjectUrl(blob_OR_source_OR_stream) =>
       JS('String',
          '(window.URL || window.webkitURL).createObjectURL(#)',
          blob_OR_source_OR_stream);
 
   static void revokeObjectUrl(String objectUrl) =>
       JS('void',
          '(window.URL || window.webkitURL).revokeObjectURL(#)', objectUrl);
 $!MEMBERS
 }