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

chromeos/chromeos.gyp

 # Copyright (c) 2012 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.
 
 {
   'variables': {
     'chromium_code': 1,
     # These files lists are shared with the GN build.
     'chromeos_sources': [
       'accelerometer/accelerometer_reader.cc',
@@ skipping 224 matching lines @@
       'login/auth/key.cc',
       'login/auth/key.h',
       'login/auth/login_performer.cc',
       'login/auth/login_performer.h',
       'login/auth/stub_authenticator.cc',
       'login/auth/stub_authenticator.h',
       'login/auth/test_attempt_state.cc',
       'login/auth/test_attempt_state.h',
       'login/auth/user_context.cc',
       'login/auth/user_context.h',
+      'login/auth/utils.cc',
+      'login/auth/utils.h',
       'login/login_state.cc',
       'login/login_state.h',
       'login/user_names.cc',
       'login/user_names.h',
       'login_event_recorder.cc',
       'login_event_recorder.h',
       'network/auto_connect_handler.cc',
       'network/auto_connect_handler.h',
       'network/certificate_pattern.cc',
       'network/certificate_pattern.h',
@@ skipping 256 matching lines @@
       'dependencies': [
         '../base/base.gyp:base',
         '../base/base.gyp:base_i18n',
         '../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
         '../build/linux/system.gyp:dbus',
         '../build/linux/system.gyp:ssl',
         '../components/components.gyp:cloud_policy_proto',
         '../components/components.gyp:device_event_log_component',
         '../components/components.gyp:onc_component',
         '../components/components.gyp:proxy_config',
+        '../components/components.gyp:user_manager',
         '../components/components.gyp:signin_core_account_id',
         '../components/prefs/prefs.gyp:prefs',
         '../crypto/crypto.gyp:crypto',
         '../dbus/dbus.gyp:dbus',
         '../google_apis/google_apis.gyp:google_apis',
         '../net/net.gyp:net',
         '../third_party/icu/icu.gyp:icui18n',
         '../third_party/libxml/libxml.gyp:libxml',
         '../third_party/protobuf/protobuf.gyp:protobuf_lite',
         '../url/url.gyp:url_lib',
@@ skipping 213 matching lines @@
             '../build/isolate.gypi',
           ],
           'sources': [
             'chromeos_unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }