Changed AuthManager::CreateAccessToken and AuthManager::ParseAccessToken

With this API we can handle expiration checks inside of AuthManager

BUG=25768507

Change-Id: I2fa5d428be6f0772d8b2656eb2bee71824f0d308
Reviewed-on: https://weave-review.googlesource.com/2030
Reviewed-by: Vitaly Buka <vitalybuka@google.com>
10 files changed