Moved most of html lib generating scripts into tools.

tools/dom/templates/html/impl/impl_DocumentFragment.darttemplate

 // 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 html;
 
 Future<CssStyleDeclaration> _emptyStyleFuture() {
   return _createMeasurementFuture(() => new Element.tag('div').style,
                                   new Completer<CssStyleDeclaration>());
 }
@@ skipping 253 matching lines @@
       "WebKit drop zone can't be set for document fragments.");
   }
 
   void set webkitRegionOverflow(String value) {
     throw new UnsupportedError(
       "WebKit region overflow can't be set for document fragments.");
   }
 
 $!MEMBERS
 }