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

chrome/browser/chromeos/login/session/user_session_manager.h

Index: chrome/browser/chromeos/login/session/user_session_manager.h
diff --git a/chrome/browser/chromeos/login/session/user_session_manager.h b/chrome/browser/chromeos/login/session/user_session_manager.h
index a428948f5da79e2d43356fa5f811b44bfce90193..9be9b718e3548d87a8e858381cb2998ee901df49 100644
--- a/chrome/browser/chromeos/login/session/user_session_manager.h
+++ b/chrome/browser/chromeos/login/session/user_session_manager.h
@@ -371,6 +371,23 @@ class UserSessionManager
     should_launch_browser_ = should_launch_browser;
   }
 
+  // The user pods display type for histogram.
+  enum UserPodsDisplay {
+    // User pods enabling or disabling is possible either via local settings or
+    // via domain policy. The former method only applies to regular devices,
+    // whereas the latter is for enterprise-managed devices. Therefore, we have
+    // four possible combiations.
+    USER_PODS_DISPLAY_ENABLED_REGULAR = 0,
+    USER_PODS_DISPLAY_ENABLED_MANAGED = 1,
+    USER_PODS_DISPLAY_DISABLED_REGULAR = 2,
+    USER_PODS_DISPLAY_DISABLED_MANAGED = 3,
+    // Maximum histogram value.
+    NUM_USER_PODS_DISPLAY = 4
+  };
+
+  // Sends metrics for user pods display when existing user has logged in.
+  void SendUserPodsMetrics();
+
   UserSessionManagerDelegate* delegate_;
 
   // Authentication/user context.