Made date input field read "mm", "dd", "yyyy", or equivalents in other languages, instead of "blank…

content/app/strings/content_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <!-- This file contains definitions of resources that will be translated for
 each locale. Specifically, these are UI strings that are used by content that
 need to be translated for each locale.-->
 
 <!-- Some of these strings and string descriptions were taken from
 WebKit/win/WebCoreLocalizedStrings.cpp so we include the original license
 below:
 
@@ skipping 526 matching lines @@
       </message>
 
       <message name="IDS_AX_AM_PM_FIELD_TEXT" desc="Accessible description of the AM/PM field in a date/time control">
         AM/PM
       </message>
 
       <message name="IDS_AX_DAY_OF_MONTH_FIELD_TEXT" desc="Accessible description of the day of month field in a date/time control">
         Day
       </message>
 
-      <message name="IDS_AX_DATE_TIME_FIELD_EMPTY_VALUE_TEXT" desc="Accessible description of empty value of field in a date/time control">
-        blank
-      </message>
-
       <message name="IDS_AX_HOUR_FIELD_TEXT" desc="Accessible description of the hour field in a date/time control">
         Hours
       </message>
 
       <message name="IDS_AX_MEDIA_DEFAULT" desc="Accessible description of a media control.">
         media control
       </message>
 
       <message name="IDS_AX_MEDIA_AUDIO_ELEMENT" desc="Accessible description of audio">
         audio
@@ skipping 303 matching lines @@
         Off
       </message>
 
       <message name="IDS_PLUGIN_INITIALIZATION_ERROR" desc="A message displayed when a plugin failed to load">
         Couldn't load plugin.
       </message>
 
     </messages>
   </release>
 </grit>