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

components/signin/core/account_id/account_id.cc

 // Copyright 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 "components/signin/core/account_id/account_id.h"
 
 #include <functional>
 
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
 #include "base/memory/singleton.h"
+#include "base/strings/string_util.h"
 #include "base/values.h"
 #include "google_apis/gaia/gaia_auth_util.h"
 
 namespace {
 
 // Known account types.
 const char kGoogle[] = "google";
 
 // Serialization keys
 const char kGaiaIdKey[] = "gaia_id";
@@ skipping 20 matching lines @@
 
   static EmptyAccountId* GetInstance() {
     return base::Singleton<EmptyAccountId>::get();
   }
 };
 
 AccountId::AccountId() {}
 
 AccountId::AccountId(const std::string& gaia_id, const std::string& user_email)
     : gaia_id_(gaia_id), user_email_(user_email) {
+  CHECK(!base::StartsWith(user_email, "g:", base::CompareCase::SENSITIVE))

[xiyuan, 2016/02/17 23:14:26]

nit: LOG_IF(FATAL, ...) or LOG_ASSERT(...)

Otherwise, the output log lines would not show up in chrome log.

[Alexander Alekseev, 2016/02/18 13:45:15]

Done.

+      << "Bad e-mail: '" << user_email << "' with gaia_id='" << gaia_id << "'";
+
   // TODO(alemate): DCHECK(!email.empty());
   // TODO(alemate): check gaia_id is not empty once it is required.
 }
 
 AccountId::AccountId(const AccountId& other)
     : gaia_id_(other.gaia_id_), user_email_(other.user_email_) {}
 
 bool AccountId::operator==(const AccountId& other) const {
   return (this == &other) ||
          (gaia_id_ == other.gaia_id_ && user_email_ == other.user_email_) ||
@@ skipping 113 matching lines @@
   return AccountId::EmptyAccountId::GetInstance()->user_id;
 }
 
 namespace BASE_HASH_NAMESPACE {
 
 std::size_t hash<AccountId>::operator()(const AccountId& user_id) const {
   return hash<std::string>()(user_id.GetUserEmail());
 }
 
 }  // namespace BASE_HASH_NAMESPACE