Remove support for the keygen tag

chrome/app/settings_strings.grdp

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Settings-specific strings (included from generated_resources.grd). -->
 <grit-part>
   <!-- About Page -->
   <message name="IDS_SETTINGS_ABOUT_PAGE_BROWSER_VERSION" desc="The text label describing the version of the browser, example: Version 57.0.2937.0 (Developer Build) unknown (64-bit)">
     Version <ph name="PRODUCT_VERSION">$1<ex>15.0.865.0</ex></ph> (<ph name="PRODUCT_CHANNEL">$2<ex>Developer Build</ex></ph>) <ph name="PRODUCT_MODIFIER">$3</ph> <ph name="PRODUCT_VERSION_BITS">$4</ph>
   </message>
   <if expr="chromeos">
     <message name="IDS_SETTINGS_ABOUT_PAGE_DETAILED_BUILD_INFO" desc="Label describing the section that shows detailed information about the current Chrome build.">
       Detailed build information
@@ skipping 1684 matching lines @@
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_COOKIES" desc="Label for the cookies site settings.">
     Cookies
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_HANDLERS" desc="Label for the protocol handlers (e.g. mailto) in site settings.">
     Handlers
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_LOCATION" desc="Label for the location site settings.">
     Location
   </message>
-  <message name="IDS_SETTINGS_SITE_SETTINGS_KEYGEN" desc="Label for the key generation site settings.">
-    Key generation
-  </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_MIC" desc="Label for the microphone site settings.">
     Microphone
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_NOTIFICATIONS" desc="Label for notifications sites site settings.">
     Notifications
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_IMAGES" desc="Label for the images site settings.">
     Images
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_JAVASCRIPT" desc="Label for the javascript site settings.">
@@ skipping 85 matching lines @@
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_HANDLERS_ASK" desc="The allow label for protocol handlers in site settings.">
     Allow sites to ask to become default handlers for protocols
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_HANDLERS_ASK_RECOMMENDED" desc="The allow label for protocol handlers in site settings (with the 'recommended' suffix).">
     Allow sites to ask to become default handlers for protocols (recommended)
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_HANDLERS_BLOCKED" desc="The block label for protocol handlers in site settings.">
     Do not allow any site to handle protocols
   </message>
-  <message name="IDS_SETTINGS_SITE_SETTINGS_KEYGEN_ALLOW" desc="The allow label for keygen in site settings.">
-    Allow all sites to use key generation in forms
-  </message>
-  <message name="IDS_SETTINGS_SITE_SETTINGS_KEYGEN_BLOCK" desc="The block label for key generation in site settings.">
-    Do not allow any site to use key generation in forms
-  </message>
-  <message name="IDS_SETTINGS_SITE_SETTINGS_KEYGEN_BLOCK_RECOMMENDED" desc="The block label for key generation in site settings (with the 'recommended' suffix).">
-    Do not allow any site to use key generation in forms (recommended)
-  </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_AUTOMATIC_DOWNLOAD_ASK" desc="The allow label for automatic download in site settings.">
     Ask when a site tries to download files automatically after the first file
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_AUTOMATIC_DOWNLOAD_ASK_RECOMMENDED" desc="The allow label for automatic download in site settings (with the 'recommended' suffix).">
     Ask when a site tries to download files automatically after the first file (recommended)
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_AUTOMATIC_DOWNLOAD_BLOCK" desc="The block label for automatic download in site settings.">
     Do not allow any site to download multiple files automatically.
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_UNSANDBOXED_PLUGINS_ASK" desc="The allow label for unsandboxed plugins in site settings.">
@@ skipping 891 matching lines @@
       System
     </message>
     <message name="IDS_SETTINGS_SYSTEM_HARDWARE_ACCELERATION_LABEL" desc="Label for the checkbox that forces Chrome to render via hardware acceleration (GPU) when available.">
       Use hardware acceleration when available
     </message>
     <message name="IDS_SETTINGS_SYSTEM_PROXY_SETTINGS_BUTTON" desc="Text for the button that changes a user's network proxy settings.">
       Change proxy settings
     </message>
   </if>
 </grit-part>