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

chrome/browser/chromeos/login/reauth_stats.h

+// 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_LOGIN_REAUTH_STATS_H_
+#define CHROME_BROWSER_CHROMEOS_LOGIN_REAUTH_STATS_H_
+
+#include <string>
+
+namespace chromeos {
+
+// Track all the ways a user may be sent through the re-auth flow.
+// This enum is used to define the buckets for an enumerated UMA histogram.
+// Hence, existing enumerated constants should never be reordered, and all new
+// constants should only be appended at the end of the  enumeration.
+enum ReauthReason {
+  // Default value: no reauth reasons were detected so far, or the reason was
+  // already reported.
+  NONE = 0,
+
+  // Legacy profile holders.
+  OTHER = 1,
+
+  // Password changed, revoked credentials, account deleted.
+  INVALID_TOKEN_HANDLE = 2,
+
+  // Incorrect password entered 3 times at the user pod.
+  INCORRECT_PASSWORD_ENTERED = 3,
+
+  // Incorrect password entered by a SAML user once.
+  // OS would show a tooltip offering user to complete the online sign-in.
+  INCORRECT_SAML_PASSWORD_ENTERED = 4,
+
+  // Device policy is set not to show user pods, which requires re-auth on every
+  // login.
+  SAML_REAUTH_POLICY = 5,
+
+  // Cryptohome is missing, most likely due to deletion during garbage
+  // collection.
+  MISSING_CRYPTOHOME = 6,
+
+  // During last login OS failed to connect to the sync with the existing RT.
+  // This could be due to account deleted, password changed, account revoked,
+  // etc.
+  SYNC_FAILED = 7,
+
+  // User cancelled the password change prompt when prompted by Chrome OS.
+  PASSWORD_UPDATE_SKIPPED = 8,
+
+  // Must be the last value in this list.
+  NUM_REAUTH_FLOW_REASONS,
+};
+
+void RecordReauthReason(const std::string& user_id, ReauthReason reason);
+void SendReauthReason(const std::string& user_id);
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_LOGIN_REAUTH_STATS_H_