MD Settings: Change some instances of "Not valid" to "Not a valid web address".

chrome/app/settings_strings.grdp

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Settings-specific strings (included from generated_resources.grd). -->
 <grit-part>
   <!-- Main Page -->
   <if expr="chromeos">
     <message name="IDS_SETTINGS_SECONDARY_USER_BANNER" desc="Banner displayed in settings page when the user is secondary in a multi-profile session.">
       Some settings belonging to <ph name="PRIMARY_EMAIL">$1<ex>john@google.com</ex></ph> are being shared with you. These settings only affect your account when using multiple sign-in.
     </message>
   </if>
 
@@ skipping 331 matching lines @@
   </message>
   <message name="IDS_SETTINGS_TOGGLE_ON" desc="Label used on a main settings toggle that is on.">
     On
   </message>
   <message name="IDS_SETTINGS_TOGGLE_OFF" desc="Label used on a main settings toggle that is ooff.">
     Off
   </message>
   <message name="IDS_SETTINGS_NOT_VALID" desc="Text indicating that an input is not valid.">
    Not valid
   </message>
+  <message name="IDS_SETTINGS_NOT_VALID_WEB_ADDRESS" desc="Text indicating that the Web address entered by the user is invalid." >
+    Not a valid web address
+  </message>
 
   <!-- Passwords and Autofill Page -->
   <message name="IDS_SETTINGS_PASSWORDS_AND_AUTOFILL_PAGE_TITLE" desc="Name of the settings page which allows managing passwords and autofill settings.">
     Passwords and forms
   </message>
   <message name="IDS_SETTINGS_AUTOFILL" desc="Name for the autofill section and toggle.">
     Autofill settings
   </message>
   <message name="IDS_SETTINGS_GOOGLE_PAYMENTS" desc="Label used to differentiate when an address or credit card entry comes from Google Payments. This should follow the casing of the 'Google Payments' brand.">
     Google Payments
@@ skipping 2595 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>