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

chromeos/cryptohome/cryptohome_parameters.cc

Index: chromeos/cryptohome/cryptohome_parameters.cc
diff --git a/chromeos/cryptohome/cryptohome_parameters.cc b/chromeos/cryptohome/cryptohome_parameters.cc
index 8b65a710e471f53b8ba07dbf8719901bd53b1643..89cd651825f3730d08839abbe2cde77af6b8c14b 100644
--- a/chromeos/cryptohome/cryptohome_parameters.cc
+++ b/chromeos/cryptohome/cryptohome_parameters.cc
@@ -8,14 +8,45 @@
 #include <stdint.h>
 
 #include "chromeos/dbus/cryptohome/key.pb.h"
+#include "components/signin/core/account_id/account_id.h"
+#include "components/user_manager/known_user.h"
 
 namespace cryptohome {
+namespace {
 
-Identification::Identification(const std::string& user_id) : user_id(user_id) {
+// Subsystem name for GaiaId migration status.
+const char kCryptohome[] = "cryptohome";
+
+const std::string GetCryptohomeId(const AccountId& account_id) {
+  // Guest/kiosk/managed/public accounts have empty GaiaId. Default to email.
+  if (account_id.GetGaiaId().empty())
+    return account_id.GetUserEmail();  // Migrated
+
+  if (GetGaiaIdMigrationStatus(account_id))
+    return account_id.GetGaiaIdKey();
+
+  return account_id.GetUserEmail();  // Migrated
+}
+
+}  //  anonymous namespace
+
+Identification::Identification() {}
+
+Identification::Identification(const AccountId& account_id)
+    : id_(GetCryptohomeId(account_id)) {}
+
+Identification::Identification(const std::string& id) : id_(id) {}
+
+Identification Identification::FromString(const std::string& id) {
+  return Identification(id);
 }
 
 bool Identification::operator==(const Identification& other) const {
-  return user_id == other.user_id;
+  return id_ == other.id_;
+}
+
+bool Identification::operator<(const Identification& right) const {
+  return id_ < right.id_;
 }
 
 KeyDefinition::AuthorizationData::Secret::Secret() : encrypt(false),
@@ -183,4 +214,23 @@ bool MountParameters::operator==(const MountParameters& other) const {
 MountParameters::~MountParameters() {
 }
 
+bool GetGaiaIdMigrationStatus(const AccountId& account_id) {
+  return user_manager::known_user::GetGaiaIdMigrationStatus(account_id,
+                                                            kCryptohome);
+}
+
+void SetGaiaIdMigrationStatusDone(const AccountId& account_id) {
+  user_manager::known_user::SetGaiaIdMigrationStatusDone(account_id,
+                                                         kCryptohome);
+}
+
 }  // namespace cryptohome
+
+namespace BASE_HASH_NAMESPACE {
+
+std::size_t hash<cryptohome::Identification>::operator()(
+    const cryptohome::Identification& cryptohome_id) const {
+  return hash<std::string>()(cryptohome_id.id());
+}
+
+}  // namespace BASE_HASH_NAMESPACE