Remove support for the keygen tag

chrome/browser/web_dev_style/css_checker.py

 # Copyright 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Presubmit script for Chromium WebUI resources.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into depot_tools, and see
 http://www.chromium.org/developers/web-development-style-guide for the rules
 we're checking against here.
@@ skipping 192 matching lines @@
                          'datetime-edit-text',
                          'datetime-edit-week-field',
                          'datetime-edit-year-field',
                          'details-marker',
                          'file-upload-button',
                          'first-letter',
                          'first-line',
                          'inner-spin-button',
                          'input-placeholder',
                          'input-speech-button',
-                         'keygen-select',
                          'media-slider-container',
                          'media-slider-thumb',
                          'meter-bar',
                          'meter-even-less-good-value',
                          'meter-inner-element',
                          'meter-optimum-value',
                          'meter-suboptimum-value',
                          'progress-bar',
                          'progress-inner-element',
                          'progress-value',
@@ skipping 197 matching lines @@
                 error += check['after'](line)
               check_errors.append(error)
           if len(check_errors) > 0:
             file_errors.append('- %s\n%s' %
                 (check['desc'], '\n'.join(check_errors)))
       if file_errors:
         results.append(self.output_api.PresubmitPromptWarning(
             '%s:\n%s' % (f[0], '\n\n'.join(file_errors))))
 
     return results