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

chromeos/BUILD.gn

 # 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.
 
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 import("//third_party/protobuf/proto_library.gni")
 
 assert(is_chromeos, "Non-ChromeOS builds must not depend on //chromeos")
 
@@ skipping 17 matching lines @@
     ":power_manager_proto",
     "//base",
     "//base:i18n",
     "//base/third_party/dynamic_annotations",
     "//components/device_event_log",
     "//components/onc",
     "//components/policy/proto",
     "//components/prefs",
     "//components/proxy_config",
     "//components/signin/core/account_id",
+    "//components/user_manager",
     "//crypto",
     "//crypto:platform",
     "//google_apis",
     "//third_party/icu",
     "//third_party/libxml",
     "//third_party/protobuf:protobuf_lite",
     "//url",
   ]
   sources = gypi_values.chromeos_sources
   defines = [ "CHROMEOS_IMPLEMENTATION" ]
@@ skipping 142 matching lines @@
   proto_out_dir = "chromeos/dbus/cryptohome"
 }
 
 proto_library("cryptohome_signkey_proto") {
   sources = [
     "//third_party/cros_system_api/dbus/cryptohome/signed_secret.proto",
   ]
 
   proto_out_dir = "chromeos/cryptohome"
 }