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

components/os_crypt/key_storage_mock.cc

Index: components/os_crypt/key_storage_mock.cc
diff --git a/components/os_crypt/key_storage_mock.cc b/components/os_crypt/key_storage_mock.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ff10b137a39f3ea7fcc2c04ad299e8f8c66f1f1f
--- /dev/null
+++ b/components/os_crypt/key_storage_mock.cc
@@ -0,0 +1,28 @@
+// Copyright 2016 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.
+
+#include <components/os_crypt/key_storage_mock.h>

[Lei Zhang, 2016/05/18 22:38:15]

Yse quotes.

[cfroussios, 2016/05/19 21:18:18]

Done.

+
+#include "base/base64.h"
+#include "base/rand_util.h"
+
+KeyStorageMock::KeyStorageMock(std::string in_key) : key_(std::move(in_key)) {}
+
+std::string KeyStorageMock::GetKey() {
+  if (key_.empty())
+    base::Base64Encode(base::RandBytesAsString(128 / 8), &key_);

[Lei Zhang, 2016/05/18 22:38:15]

Ditto, is "128 / 8" necessary?

[cfroussios, 2016/05/19 21:18:18]

Done.

[Lei Zhang, 2016/05/19 22:45:38]

Wait, you kept it in the other place where I asked the same question. Please be
consistent.

[cfroussios, 2016/05/20 16:44:52]

Done.

+  return key_;
+}
+
+bool KeyStorageMock::Init() {
+  return true;
+}
+
+void KeyStorageMock::ResetTo(std::string new_key) {

[Lei Zhang, 2016/05/18 22:38:15]

How about making the parameter a base::StringPiece instead? And add a Clear()
method instead of calling ResetTo(std::string()))?

[cfroussios, 2016/05/19 21:18:18]

Done.

+  key_ = std::move(new_key);
+}
+
+std::string* KeyStorageMock::GetKeyPtr() {
+  return &key_;
+}