Add new Chrome OS key type: Salted SHA256

Add new Chrome OS key type: Salted SHA256

This CL adds a new key type for Chrome OS authentication and cryptohome
encryption, a base64-encoded salted SHA256 hash. This will be the first
key type supported by the credentials passing API.

BUG=367847
TEST=Extended unit test

Committed: https://crrev.com/28dae509e63d445a8780450f2e9152fb68ad74b8
Cr-Commit-Position: refs/heads/master@{#292924}

[bartfab (slow), 2014-08-28 10:17:42]

bartfab@chromium.org changed reviewers:
+ antrim@chromium.org

[bartfab (slow), 2014-08-28 10:17:42]

Hi Denis,

Could you take a look please?

[bartfab (slow), 2014-09-01 08:57:57]

Hi Denis,

Friendly review ping.

[bartfab (slow), 2014-09-02 12:29:35]

bartfab@chromium.org changed reviewers:
+ dzhioev@chromium.org
- antrim@chromium.org

[bartfab (slow), 2014-09-02 12:29:36]

Hi Pavel,

It looks like Denis may be out. Could you take a look?

[dzhioev (left Google), 2014-09-02 13:33:49]

On 2014/09/02 12:29:36, bartfab wrote:
> Hi Pavel,
> 
> It looks like Denis may be out. Could you take a look?

LGTM

[bartfab (slow), 2014-09-02 13:40:13]

The CQ bit was checked by bartfab@chromium.org

[commit-bot: I haz the power, 2014-09-02 13:42:11]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/bartfab@chromium.org/515153002/1

[commit-bot: I haz the power, 2014-09-02 14:41:48]

Committed patchset #1 (id:1) as 0f1ecad70597a2542150f20ea8b628b4eb28bae7

[commit-bot: I haz the power, 2014-09-10 03:18:25]

Patchset 1 (id:??) landed as
https://crrev.com/28dae509e63d445a8780450f2e9152fb68ad74b8
Cr-Commit-Position: refs/heads/master@{#292924}