NSS is no longer an option as the cryptographic service
provider - all platforms have transitioned to using BoringSSL. Any remaining files in crypto/ that use NSS will always have USE_NSS_CERTS set.

This also fixes some unit tests that used the wrong ifdefs once
everything was converted to use BoringSSL.

BUG=604728

Review-Url: https://codereview.chromium.org/2046863002
Cr-Commit-Position: refs/heads/master@{#398348}