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

chromeos/cryptohome/cryptohome_parameters.h

 // Copyright 2014 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 CHROMEOS_CRYPTOHOME_CRYPTOHOME_PARAMETERS_H_
 #define CHROMEOS_CRYPTOHOME_CRYPTOHOME_PARAMETERS_H_
 
 #include <stdint.h>
 
 #include <string>
 #include <vector>
 
+#include "base/containers/hash_tables.h"
 #include "base/memory/scoped_ptr.h"
 #include "chromeos/chromeos_export.h"
 
+class AccountId;
+
 namespace cryptohome {
 
 enum AuthKeyPrivileges {
   PRIV_MOUNT = 1 << 0,              // Can mount with this key.
   PRIV_ADD = 1 << 1,                // Can add new keys.
   PRIV_REMOVE = 1 << 2,             // Can remove other keys.
   PRIV_MIGRATE = 1 << 3,            // Destroy all keys and replace with new.
   PRIV_AUTHORIZED_UPDATE = 1 << 4,  // Key can be updated in place.
   PRIV_DEFAULT = PRIV_MOUNT | PRIV_ADD | PRIV_REMOVE | PRIV_MIGRATE
 };
 
 // Identification of the user calling cryptohome method.
-struct CHROMEOS_EXPORT Identification {
-  explicit Identification(const std::string& user_id);
+class CHROMEOS_EXPORT Identification {
+ public:
+  Identification();
+
+  explicit Identification(const AccountId& account_id);
 
   bool operator==(const Identification& other) const;
 
-  std::string user_id;
+  // This method should be used for migration purpose only.
+  static Identification FromString(const std::string& id);
+
+  const std::string& id() const { return id_; }
+
+  bool operator<(const Identification& right) const;
+
+ private:
+  explicit Identification(const std::string&);
+
+  std::string id_;
 };
 
 // Definition of the key (e.g. password) for the cryptohome.
 // It contains authorization data along with extra parameters like permissions
 // associated with this key.
 struct CHROMEOS_EXPORT KeyDefinition {
   enum Type {
     TYPE_PASSWORD = 0
   };
 
@@ skipping 94 matching lines @@
 
   // If |true|, the mounted home dir will be backed by tmpfs. If |false|, the
   // ephemeral users policy decides whether tmpfs or an encrypted directory is
   // used as the backend.
   bool ephemeral;
 
   // If not empty, home dir will be created with these keys if it exist.
   std::vector<KeyDefinition> create_keys;
 };
 
+// This function returns true if cryptohome of |account_id| is migrated to
+// gaiaId-based identifier (AccountId::GetGaiaIdKey()).
+bool GetGaiaIdMigrationStatus(const AccountId& account_id);
+
+// This function marks |account_id| cryptohome migrated to gaiaId-based
+// identifier (AccountId::GetGaiaIdKey()).
+void SetGaiaIdMigrationStatusDone(const AccountId& account_id);
+
 }  // namespace cryptohome
 
+namespace BASE_HASH_NAMESPACE {
+
+// Implement hashing of cryptohome::Identification, so it can be used as a key
+// in STL containers.
+template <>
+struct hash<cryptohome::Identification> {
+  std::size_t operator()(const cryptohome::Identification& cryptohome_id) const;
+};
+
+}  // namespace BASE_HASH_NAMESPACE
+
 #endif  // CHROMEOS_CRYPTOHOME_CRYPTOHOME_PARAMETERS_H_