Add the new UMA key 'Translate.LocalesOnDisabledByPrefs'.

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 9340 matching lines @@
 </histogram>
 
 <histogram name="Translate.LanguageVerification"
     enum="TranslateLanguageVerification">
   <summary>
     For each page load, measures whether the provided Content-Language header
     matches the language determined by CLD.
   </summary>
 </histogram>
 
+<histogram name="Translate.LocalesOnDisabledByPrefs" enum="LanguageCode">
+  <summary>
+    Logs the user locale when the Translate feature is disabled by the user.
+    This is recorded each time a webpage is loaded and prefs for translation is
+    checked. This allows us to investigate the correlation between the user
+    locale and the usage rates of the Translate.
+  </summary>
+</histogram>
+
 <histogram name="Translate.PageScheme" enum="TranslateScheme">
   <summary>Counts translation target page schemes.</summary>
 </histogram>
 
 <histogram name="Translate.RevertTranslation">
   <summary>
     The number of times the show original button was clicked in the translate
     infobar.
   </summary>
 </histogram>
@@ skipping 7072 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>