Identity API: Add token cache and identity.invalidateAuthToken.

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 4296 matching lines @@
   <int value="429" label="SYNCFILESYSTEM_GETCONFLICTRESOLUTIONPOLICY"/>
   <int value="430" label="NETWORKINGPRIVATE_SETPROPERTIES"/>
   <int value="431" label="NETWORKINGPRIVATE_GETSTATE"/>
   <int value="432" label="POWER_REQUESTKEEPAWAKE"/>
   <int value="433" label="POWER_RELEASEKEEPAWAKE"/>
   <int value="434" label="WALLPAPERPRIVATE_SETCUSTOMWALLPAPERLAYOUT"/>
   <int value="435" label="DOWNLOADSINTERNAL_DETERMINEFILENAME"/>
   <int value="436" label="SYNCFILESYSTEM_GETFILESYNCSTATUSES"/>
   <int value="437" label="MEDIAGALLERIESPRIVATE_GETHANDLERS"/>
   <int value="438" label="WALLPAPERPRIVATE_RESETWALLPAPER"/>
+  <int value="439" label="EXPERIMENTAL_IDENTITY_INVALIDATEAUTHTOKEN"/>
 </enum>
 
 <enum name="FallbackSSLVersion" type="int">
   <int value="0" label="FALLBACK_NONE">SSL version fallback did not occur.</int>
   <int value="1" label="FALLBACK_SSL3">Fell back on SSL 3.0.</int>
   <int value="2" label="FALLBACK_TLS1">Fell back on TLS 1.0.</int>
   <int value="3" label="FALLBACK_TLS1_1">Fell back on TLS 1.1.</int>
 </enum>
 
 <enum name="FtpDataConnectionError" type="int">
@@ skipping 1249 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>