Add a histogram definition for Linux.GlibcVersion.

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 475 matching lines @@
   <summary>Errno of errors encountered in WritableFileFlush.</summary>
 </histogram>
 
 <histogram name="LevelDBEnv.TimeTo" units="milliseconds">
   <summary>
     Time Non-IDB LevelDBEnv slept before successfully completing this operation.
     0 means success on the first try.
   </summary>
 </histogram>
 
+<histogram name="Linux.GlibcVersion" enum="LinuxGlibcVersion">
+  <summary>The version of glibc used. (Linux only)</summary>
+</histogram>
+
 <histogram name="Media.DetectedAudioCodec" enum="FFmpegCodecs">
   <summary>Audio codec used in HTML5 media.</summary>
 </histogram>
 
 <histogram name="Media.DetectedVideoCodec" enum="FFmpegCodecs">
   <summary>Video codec used in HTML5 media.</summary>
 </histogram>
 
 <histogram name="Navigation.MainFrameScheme" enum="NavigationScheme">
   <summary>The scheme of the URL for each main-frame navigation.</summary>
@@ skipping 5064 matching lines @@
   <int value="11" label="CreateDir"/>
   <int value="12" label="DeleteDir"/>
   <int value="13" label="GetFileSize"/>
   <int value="14" label="Renamefile"/>
   <int value="15" label="LockFile"/>
   <int value="16" label="UnlockFile"/>
   <int value="17" label="GetTestDirectory"/>
   <int value="18" label="NewLogger"/>
 </enum>
 
+<enum name="LinuxGlibcVersion" type="int">
+  <int value="0" label="Not Parseable"/>
+  <int value="1" label="Unknown"/>
+  <int value="2" label="2.11"/>
+  <int value="3" label="2.12"/>
+  <int value="4" label="2.13"/>
+  <int value="5" label="2.14"/>
+  <int value="6" label="2.15"/>
+  <int value="7" label="2.16"/>
+  <int value="8" label="2.17"/>
+  <int value="9" label="2.18"/>
+  <int value="10" label="2.19"/>
+</enum>
+
 <enum name="LoadType" type="int">
   <int value="0" label="UNDEFINED_LOAD">Not yet initialized</int>
   <int value="1" label="RELOAD">User pressed reload</int>
   <int value="2" label="HISTORY_LOAD">Back or forward</int>
   <int value="3" label="NORMAL_LOAD">User entered URL, or omnibox search</int>
   <int value="4" label="LINK_LOAD">(deprecated) Included next 4 categories</int>
   <int value="5" label="LINK_LOAD_NORMAL">Commonly following of link</int>
   <int value="6" label="LINK_LOAD_RELOAD">JS/link directed reload</int>
   <int value="7" label="LINK_LOAD_CACHE_STALE_OK">
     back/forward or encoding change
@@ skipping 1733 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>