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.

[Ilya Sherman, 2015/04/28 20:07:18]

Please document that this enum is used to back a histogram, and thus should be
treated as append-only

[Ivan Podogov, 2015/04/29 10:34:24]

Done.

+enum ReauthReason {
+  // Default value: no reauth reasons were detected so far, or the reason was
+  // already reported.
+  NONE = 0,
+  // Password changed, revoked credentials, account deleted.

[Nikita (slow), 2015/04/29 09:21:46]

nit: insert empty line before comment here and below.

[Ivan Podogov, 2015/04/29 10:34:24]

Done.

+  INVALID_TOKEN_HANDLE,

[Nikita (slow), 2015/04/29 09:21:46]

Set explicit int value for each of these enum constants so that when one of
these is deprecated others that follow it won't change their int values.

[Ivan Podogov, 2015/04/29 10:34:24]

Done.

+  // Incorrect password entered 3 times at the user pod.
+  INCORRECT_PASSWORD_ENTERED,
+  // 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,
+  // Device policy is set not to show user pods, which requires re-auth on every
+  // login.
+  SAML_REAUTH_POLICY,
+  // Cryptohome is missing, most likely due to deletion during garbage
+  // collection.
+  MISSING_CRYPTOHOME,
+  // 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,
+  // User cancelled the password change prompt when prompted by Chrome OS.
+  PASSWORD_UPDATE_SKIPPED,
+  // Legacy profile holders.
+  OTHER,

[Ilya Sherman, 2015/04/28 20:07:18]

nit: It's typically best to list "other" at the beginning of the list.  That
way, if you ever add additional items to the list, "other" remains at one of the
ends of the list, rather than getting buried in the middle somewhere.

[Ivan Podogov, 2015/04/29 10:34:24]

Done.

+  // 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_