Remove support for the keygen tag

third_party/WebKit/Source/core/css/html.css

 /*
  * The default style sheet used to render HTML.
  *
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 373 matching lines @@
     -webkit-padding-after: 0.625em;
     border: 2px groove ThreeDFace;
     min-width: -webkit-min-content;
 }
 
 button {
     -webkit-appearance: button;
 }
 
 /* Form controls don't go vertical. */
-input, textarea, keygen, select, button, meter, progress {
+input, textarea, select, button, meter, progress {
     -webkit-writing-mode: horizontal-tb !important;
 }
 
-input, textarea, keygen, select, button {
+input, textarea, select, button {
     margin: 0__qem;
     font: -webkit-small-control;
     text-rendering: auto; /* FIXME: Remove when tabs work with optimizeLegibility. */
     color: initial;
     letter-spacing: normal;
     word-spacing: normal;
     line-height: normal;
     text-transform: none;
     text-indent: 0;
     text-shadow: none;
@@ skipping 67 matching lines @@
     -webkit-user-modify: read-only !important;
     opacity: 0;
     pointer-events: none;
 }
 
 input:enabled:read-write:-webkit-any(:focus,:hover)::-webkit-inner-spin-button {
     opacity: 1;
     pointer-events: auto;
 }
 
-keygen, select {
+select {
     border-radius: 5px;
 }
 
-keygen::-webkit-keygen-select {
-    margin: 0px;
-}
-
 textarea {
     -webkit-appearance: textarea;
     background-color: white;
     border: 1px solid;
     -webkit-rtl-ordering: logical;
     -webkit-user-select: text;
     flex-direction: column;
     resize: auto;
     cursor: auto;
     padding: 2px;
@@ skipping 98 matching lines @@
 
 input[type="range" i]::-webkit-slider-thumb, input[type="range" i]::-webkit-media-slider-thumb {
     -webkit-appearance: sliderthumb-horizontal;
     box-sizing: border-box;
     -webkit-user-modify: read-only !important;
     display: block;
 }
 
 input[type="button" i]:disabled, input[type="submit" i]:disabled, input[type="reset" i]:disabled,
 input[type="file" i]:disabled::-webkit-file-upload-button, button:disabled,
-select:disabled, keygen:disabled, optgroup:disabled, option:disabled,
+select:disabled, optgroup:disabled, option:disabled,
 select[disabled]>option {
     color: GrayText
 }
 
 input[type="button" i]:active, input[type="submit" i]:active, input[type="reset" i]:active, input[type="file" i]:active::-webkit-file-upload-button, button:active {
     border-style: inset
 }
 
 input[type="button" i]:active:disabled, input[type="submit" i]:active:disabled, input[type="reset" i]:active:disabled, input[type="file" i]:active:disabled::-webkit-file-upload-button, button:active:disabled {
     border-style: outset
@@ skipping 347 matching lines @@
 
 /* Read-only text fields do not show a focus ring but do still receive focus */
 html:focus, body:focus, input[readonly]:focus {
     outline: none
 }
 
 embed:focus, iframe:focus, object:focus {
     outline: none
 }
 
-input:focus, textarea:focus, keygen:focus, select:focus {
+input:focus, textarea:focus, select:focus {
     outline-offset: -2px
 }
 
 input[type="button" i]:focus,
 input[type="checkbox" i]:focus,
 input[type="file" i]:focus,
 input[type="hidden" i]:focus,
 input[type="image" i]:focus,
 input[type="radio" i]:focus,
 input[type="reset" i]:focus,
@@ skipping 121 matching lines @@
     padding: 0px;
     border-width: 0px;
 }
 
 /* Allows thead sections to print at the top of each page. */
 @media print {
     thead { break-inside:avoid; }
 }
 
 /* noscript is handled internally, as it depends on settings. */