ChromeOS cryptohome should be able to use gaia id as user identifier.

chromeos/login/auth/utils.cc

+// Copyright 2016 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 "chromeos/login/auth/utils.h"
+
+#include "chromeos/cryptohome/cryptohome_parameters.h"
+#include "components/signin/core/account_id/account_id.h"
+#include "components/user_manager/known_user.h"
+
+namespace cryptohome {
+
+class AccountId GetAccountId(const Identification& user_id) {
+  const std::vector<AccountId> known_account_ids =
+      user_manager::known_user::GetKnownAccountIds();
+
+  for (const AccountId& known_id : known_account_ids) {
+    if (known_id.GetGaiaIdKey() == user_id.id())
+      return known_id;
+  }
+
+  return user_manager::known_user::GetAccountId(user_id.id(),
+                                                std::string() /* gaia_id */);
+}

[stevenjb, 2016/02/23 19:27:34]

This is a strange place to put something in the cryptohome namespace. Also both
'utils.cc' and 'GetAccountId' are too generic.

It looks like this should really be:

user_manager::known_user::GetKnownIdFromUserId(user_id.id())

i.e. I don't see any reason why we should pass cryptohome::Identification to the
helper instead of cryptohome::Identification.id()

[Alexander Alekseev, 2016/02/24 01:52:57]

First of all, one of the important steps in this CL was moving away from
std::string when passing cryptohome id to chromeos/dbus/* . as you could see,
the first version of this CL didn't have this change. And I found a lot of code
I missed when incorrect ID stopped compiling. So this is done to prevent errors
in coding.

I needed some structure that could represent user ID in dbus/. It also should be
AccounId-constructible (which requires access to IsGaiaIdMigrationStarted , i.e.
chromeos internals ). So the cryptohome::Identifier suits here very well.

Reverse translation requires access to chromeos and user_manager. But
UserManager must not depend on ChromeOS, so I put the translation here.

Why is it strange to put this tranlation here as there is a lot of code in
chromeos/login/auth that belongs to cryptohome?

[stevenjb, 2016/02/24 17:25:43]

I do not see a single instance of "namespace cryptohome" in src/chromeos/login,
and I find its use here very confusing.

I understand your argument for passing in cryptohome::Identification, but this
does not seem like the best place for this glue code. 

Why not make this cryptohome::Identification::GetAccountId()? You are already
have all of the same dependencies there.

[Alexander Alekseev, 2016/02/25 07:40:46]

Done.

+
+}  // namespace cryptohome