OSCrypt for POSIX uses libsecret to store a randomised encryption key.

components/os_crypt.gypi

 # 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.
 
 {
   'targets': [
     {
       'target_name': 'os_crypt',
       'type': 'static_library',
       'include_dirs': [
@@ skipping 36 matching lines @@
               'AdditionalDependencies': [
                 'crypt32.lib',
               ],
             },
           },
         }],
         ['OS=="linux" and chromeos!=1', {
           'sources': [ 
             'os_crypt/libsecret_util_posix.cc',
             'os_crypt/libsecret_util_posix.h',
+            'os_crypt/key_storage_linux.cc',
+            'os_crypt/key_storage_linux.h',
+            'os_crypt/os_crypt_linux.cc',
+          ],
+          'sources!': [
+            'os_crypt/os_crypt_posix.cc',
           ],
           'defines': [
             'USE_LIBSECRET',
           ],
           'include_dirs' : [
             '../third_party/libsecret/'
           ],
           'dependencies': [
             '../build/linux/system.gyp:glib',
           ],
         }],
       ],
       'target_conditions': [
         ['OS=="ios"', {
           'sources/': [
             ['include', '^os_crypt/keychain_password_mac\\.mm$'],
             ['include', '^os_crypt/os_crypt_mac\\.mm$'],
           ],
         }],
       ],
     },
   ],
 }