Site Settings Desktop: Implement tri-state 'Delete local data on exit'.

chrome/app/settings_strings.grdp

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Settings-specific strings (included from generated_resources.grd). -->
 <grit-part>
   <!-- About Page -->
   <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
     </message>
     <message name="IDS_SETTINGS_ABOUT_PAGE_ARC_VERSION" desc="Label for ARC version">
       ARC Version
@@ skipping 1701 matching lines @@
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_COOKIE_REMOVE_ALL" desc="Label for the button to delete all cookies for a site.">
     Remove All
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_THIRD_PARTY_COOKIE" desc="Label for the Block 3rd-party cookie checkbox on the Cookies category.">
     Block third-party cookies.
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_THIRD_PARTY_COOKIE_SUBLABEL" desc="A sub-label below the Block 3rd-party cookie checkbox.">
     Prevent third-party websites from saving and reading cookie data.
   </message>
+  <message name="IDS_SETTINGS_SITE_SETTINGS_DELETE_DATA_POST_SESSION" desc="Label for the checkbox that allows the user to automatically delete their data at the end of the browser session.">
+    Keep local data only until you quit your browser
+  </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_ADOBE_FLASH_SETTINGS" desc="The text for the link that points the user to the Adobe Flash Player Storage settings on the web">
     Adobe Flash Player Storage settings
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_LEARN_MORE" desc="The text for the link to learn more about how managing exceptions work for Site Settings categories">
     Learn more
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_HANDLER_IS_DEFAULT" desc="A label showing that a certain handler for a given protocol is the default.">
     Default
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_HANDLER_SET_DEFAULT" desc="A label for the action of making a certain handler the default for a given protocol.">
@@ skipping 534 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>