Add a11y virtual keyboard icon when a11y VK is enabled

ash/ash_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <!--
 This file contains the strings for ash.
 -->
 
 <grit base_dir="." latest_public_release="0" current_release="1"
       source_lang_id="en" enc_check="möl">
   <outputs>
     <output filename="grit/ash_strings.h" type="rc_header">
@@ skipping 506 matching lines @@
       </message>
 
       <message name="IDS_ASH_STATUS_TRAY_LOCALLY_MANAGED_LABEL" desc="Label shown instead of email for supervised users">
          Supervised user
       </message>
 
       <message name="IDS_ASH_STATUS_TRAY_PREVIOUS_MENU" desc="The accessible text for header entries for detailed versions of status tray items.">
         Previous menu
       </message>
 
+      <message name="IDS_ASH_VIRTUAL_KEYBOARD_TRAY_ACCESSIBLE_NAME" desc="The accessible text for virtual keyboard icon in status tray.">
+        Show on-screen keyboard
+      </message>
+
       <message name="IDS_ASH_NOTIFICATION_UNREAD_COUNT_NINE_PLUS" desc="The text shown in the notification icon for the unread count when the count is more than 9.">
         9+
       </message>
       <message name="IDS_ASH_MAXIMIZE_WINDOW" desc="A help text to show that when the button gets clicked the window get maximized.">
         Maximize
       </message>
       <message name="IDS_ASH_SNAP_WINDOW_RIGHT" desc="A help text to show that when the button gets clicked the window get snapped to the right side.">
         Right
       </message>
       <message name="IDS_ASH_SNAP_WINDOW_LEFT" desc="A help text to show that when the button gets clicked the window get snapped to the left side.">
@@ skipping 82 matching lines @@
 
       <!-- ChromeOS-specific strings -->
       <if expr="chromeos">
         <part file="ash_chromeos_strings.grdp" />
       </if>
 
     </messages>
   </release>
 </grit>