Add an UMA stat to be able to see if the User pods are show on start screen,

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index bd419fd674f4a9a1442618fbeaa1c12f88959c5a..c41a4d1e5d6525a2164d44ad2562fc31036bdce6 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -42268,6 +42268,14 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="UserSessionManager.UserPodsDisplay" enum="UserPodsDisplay">
+  <owner>ginkage@chromium.org</owner>
+  <summary>
+    Whether the user pods were enabled during login, and what could disable
+    them.
+  </summary>
+</histogram>
+
 <histogram name="V8.ASTOptimization">
   <obsolete>
     This histogram is no longer present in V8.
@@ -62395,6 +62403,13 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="0" label="WiFi Scan"/>
 </enum>
 
+<enum name="UserPodsDisplay" type="int">
+  <int value="0" label="Enabled by local settings"/>
+  <int value="1" label="Enabled by domain policy"/>
+  <int value="2" label="Disabled by local settings"/>
+  <int value="3" label="Disabled by domain policy"/>
+</enum>
+
 <enum name="UserSelectableSyncType" type="int">
   <int value="0" label="Bookmarks"/>
   <int value="1" label="Preferences"/>