Implement pin storage backend.

chrome/browser/chromeos/login/quick_unlock/pin_authentication.h

+// 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_LOGIN_QUICK_UNLOCK_PIN_AUTHENTICATION_H_
+#define CHROME_BROWSER_CHROMEOS_LOGIN_QUICK_UNLOCK_PIN_AUTHENTICATION_H_
+
+#include <string>
+
+namespace chromeos {
+
+class PinStorage;
+
+// Is PIN entry available for the given user?
+bool IsPinAvailable(PinStorage* storage);

[achuithb, 2016/05/13 23:34:56]

These should be in a new namespace nested in chromeos, I believe.

Why are these not just methods of PinStorage?

[stevenjb, 2016/05/16 16:33:34]

+1

[jdufault, 2016/05/16 22:08:47]

I wanted to keep them separate because conceptually storing and authenticating
against the pin are separate concepts, but I suppose the storage code already
deals with generating the salt/etc, so I've merged the two files.

+
+// Returns true if the given PIN is valid and the user is allowed to submit a
+// PIN (ie, no auth attempt will be made if IsPinAvailable returns false).
+bool IsValidPin(PinStorage* storage, const std::string& raw_pin);
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_LOGIN_QUICK_UNLOCK_PIN_AUTHENTICATION_H_