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 34 matching lines @@
           'msvs_settings': {
             'VCLinkerTool': {
               'AdditionalDependencies': [
                 'crypt32.lib',
               ],
             },
           },
         }],
         ['OS=="linux" and chromeos!=1 and use_glib==1', {
           'sources': [
-            'os_crypt/libsecret_util_posix.cc',
-            'os_crypt/libsecret_util_posix.h',
+            'os_crypt/key_storage_libsecret.cc',
+            'os_crypt/key_storage_libsecret.h',
+            'os_crypt/key_storage_linux.cc',
+            'os_crypt/key_storage_linux.h',
+            'os_crypt/libsecret_util_linux.cc',
+            'os_crypt/libsecret_util_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$'],
             ['include', '^os_crypt/os_crypt_mac\\.mm$'],
           ],
         }],
       ],
     },
     {
       'target_name': 'os_crypt_test_support',
       'type': 'static_library',
       'sources': [
-        "os_crypt/os_crypt_mocker.cc",
-        "os_crypt/os_crypt_mocker.h",
+        'os_crypt/os_crypt_mocker.cc',
+        'os_crypt/os_crypt_mocker.h',
       ],
       'dependencies': [
         '../base/base.gyp:base',
+        '../testing/gtest.gyp:gtest',
       ],
       'conditions': [
         ['OS=="linux" and chromeos!=1 and use_glib==1', {
+          'sources': [
+            'os_crypt/os_crypt_mocker_linux.cc',
+            'os_crypt/os_crypt_mocker_linux.h',
+          ],
           'defines': [
             'USE_LIBSECRET',
           ],
           'include_dirs' : [
             '../third_party/libsecret/'
           ],
           'dependencies': [
             '../build/linux/system.gyp:glib',
           ],
         }],
       ]
     }
   ],
 }