UMA to track the reason for re-auth (draft).

chrome/browser/chromeos/login/reauth_stats.cc

+// Copyright (c) 2015 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.
+
+#include "chrome/browser/chromeos/login/reauth_stats.h"
+
+#include "base/metrics/histogram_macros.h"
+#include "components/user_manager/user_manager.h"
+
+namespace chromeos {
+
+void RecordReauthReason(const std::string& user_id, ReauthReason reason) {
+  user_manager::UserManager* user_manager = user_manager::UserManager::Get();
+  int old_reason;
+  // We record only the first value, skipping everything else, except "none"
+  // value, which is used to reset the current state.
+  if (!user_manager->FindReauthReason(user_id, &old_reason) ||
+      (static_cast<ReauthReason>(old_reason) == ReauthReason::NONE &&
+       reason != ReauthReason::NONE)) {
+    user_manager->UpdateReauthReason(user_id, static_cast<int>(reason));
+  }
+}
+
+void SendReauthReason(const std::string& user_id) {
+  user_manager::UserManager* user_manager = user_manager::UserManager::Get();
+  int reauth_reason;
+  if (user_manager->FindReauthReason(user_id, &reauth_reason) &&
+      static_cast<ReauthReason>(reauth_reason) != ReauthReason::NONE) {
+    UMA_HISTOGRAM_ENUMERATION("Login.ReauthReason", reauth_reason,
+                              NUM_REAUTH_FLOW_REASONS);
+    user_manager->UpdateReauthReason(user_id,
+                                     static_cast<int>(ReauthReason::NONE));
+  }
+}
+
+}  // namespace chromeos