Revert "Adding constructor to ContentElement."

lib/html/scripts/systemhtml.py

 #!/usr/bin/python
 # 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.
 
 """This module provides shared functionality for the system to generate
 Dart:html APIs from the IDL database."""
 
 import emitter
 
@@ skipping 243 matching lines @@
     ElementConstructorInfo(tag='a', opt_params=[('String', 'href')]),
   'AreaElement': 'area',
   'ButtonElement': 'button',
   'BRElement': 'br',
   'BaseElement': 'base',
   'BodyElement': 'body',
   'ButtonElement': 'button',
   'CanvasElement':
     ElementConstructorInfo(tag='canvas',
                            opt_params=[('int', 'width'), ('int', 'height')]),
-  'ContentElement': 'content',
   'DataListElement': 'datalist',
   'DListElement': 'dl',
   'DetailsElement': 'details',
   'DivElement': 'div',
   'EmbedElement': 'embed',
   'FieldSetElement': 'fieldset',
   'FormElement': 'form',
   'HRElement': 'hr',
   'HeadElement': 'head',
   'HeadingElement': [ElementConstructorInfo('h1'),
@@ skipping 956 matching lines @@
   def GenerateLibraries(self, dart_files):
     auxiliary_dir = os.path.relpath(self._auxiliary_dir, self._output_dir)
     self._GenerateLibFile(
         'html_dart2js.darttemplate',
         os.path.join(self._output_dir, 'html_dart2js.dart'),
         dart_files,
         AUXILIARY_DIR=systembase.MassagePath(auxiliary_dir))
 
   def Finish(self):
     pass