I'm working on some changes to XsrfTokenManager (b/35388772) and ServerSecret
was crufty enough that I ended up rewriting it. Now it uses a LoadingCache
with a transaction instead of needlessly race-condition-y static init logic.
It also now supports retrieving its value as either a UUID (the old format
used by XsrfTokenManager) or a byte[]. The latter is more flexible and can
be directly used with HMAC which the new XsrfTokenManager format will employ.
And lastly, I added tests. In addition, I tested this code on alpha and
verified appropriate operation (XSRF tokens still work from the console and
from regtool; if you remove ServerSecret from datastore and memcache, it
persists a new one).
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=148931620
