Translate: Filter and record languages whose names Chrome doesn't show

tools/metrics/histograms/histograms.xml

 <!--
 Copyright 2013 The Chromium Authors. All rights reserved.
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 -->
 
 <!--
 This file is used to generate a comprehensive list of Chrome histograms along
 with a detailed description for each histogram.
 
@@ skipping 9377 matching lines @@
   <summary>
     The time from injecting scripts for Chrome Translate to the finishing loads
     of all depending libraries.
   </summary>
 </histogram>
 
 <histogram name="Translate.TimeToTranslate" units="milliseconds">
   <summary>The time from starting translation to the completion.</summary>
 </histogram>
 
+<histogram name="Translate.UndisplayableLanguage" enum="LanguageCode">
+  <summary>
+    Logs an undisplayable language are included in the language list sent by the
+    Translate server. The Translate server sends the list each time the user
+    runs Chrome. This metrics tells us that there is a language which UI should
+    deal with but doesn't.
+  </summary>
+</histogram>
+
 <histogram name="Translate.UnsupportedLanguageAtInitiation" enum="LanguageCode">
   <summary>
     Logs an unsupported source language detected during initiation of the
     Translate feature.  This is reported when the language detector successfully
     detects the language of the webpage, but the language is not supported by
     the translation server because it is too minor.  This metric allows us to
     assess how important the unsupported language is for Google translate.
   </summary>
 </histogram>
 
@@ skipping 7035 matching lines @@
 <fieldtrial name="SSLResumption">
   <group name="Resume_Handshake" label="Session Resumption"/>
   <group name="Full_Handshake" label="Full"/>
   <affected-histogram name="Net.SSL_Connection_Latency"/>
   <affected-histogram name="Net.SSL_Connection_Latency_Google"/>
 </fieldtrial>
 
 </fieldtrials>
 
 </histogram-configuration>