Add ash UI for third-party VPNs

ui/chromeos/ui_chromeos_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <grit base_dir="." latest_public_release="0" current_release="1"
       source_lang_id="en" enc_check="möl">
   <outputs>
     <output filename="grit/ui_chromeos_strings.h" type="rc_header">
       <emit emit_type='prepend'></emit>
     </output>
     <output filename="ui_chromeos_strings_am.pak" type="data_package" lang="am" />
     <output filename="ui_chromeos_strings_ar.pak" type="data_package" lang="ar" />
@@ skipping 113 matching lines @@
       <message name="IDS_ASH_STATUS_TRAY_NETWORK_LIST_ACTIVATING" desc="Message for the network list when activating a network.">
         <ph name="NAME">$1<ex>YBH Cellular</ex></ph>: Activating...
       </message>
       <message name="IDS_ASH_STATUS_TRAY_NETWORK_LIST_CONNECTING" desc="Message for the network list when connecting to a network.">
         <ph name="NAME">$1<ex>GoogleGuest</ex></ph>: Connecting...
       </message>
       <message name="IDS_ASH_STATUS_TRAY_NETWORK_NOT_CONNECTED" desc="Description in status area or network dropdown when no network is connected.">
         No network
       </message>
 
-      <message name="IDS_ASH_STATUS_TRAY_NETWORK_NO_VPN" desc="The label used in the tray popup to notify no vpn is configured.">
-        VPN is not configured.
-      </message>
       <message name="IDS_ASH_STATUS_TRAY_NO_NETWORKS" desc="The message to display in the network info bubble when it is otherwise empty.">
         No network information available
       </message>
       <message name="IDS_ASH_STATUS_TRAY_NO_CELLULAR_NETWORKS" desc="The message to display in the network list when no cellular networks are available.">
         No cellular network available
       </message>
       <message name="IDS_ASH_STATUS_TRAY_VPN_DISCONNECTED" desc="The label used in system tray bubble to display vpn is disconnected.">
         VPN disconnected
       </message>
       <message name="IDS_ASH_STATUS_TRAY_NETWORK_WIFI_ENABLED" desc="The label used in the tray popup to notify that Wi-Fi is turned on.">
@@ skipping 332 matching lines @@
       <message name="IDS_NETWORK_ACTIVATION_ERROR_TITLE" desc="Title for network activation error notification">
         Network Activation Error
       </message>
       <message name="IDS_NETWORK_ACTIVATION_NEEDS_CONNECTION" desc="Message when attempting to activate a mobile network that requires a connection">
         Activation of '<ph name="name">$1<ex>Generic Wireless</ex></ph>' requires a network connection.
       </message>
 
     </messages>
   </release>
 </grit>