PSA: iOS is now using BoringSSL on Trunk

[Steven Valdez]

Hi all,

For those of you syncing your checkouts, as of https://crrev.com/387011, the iOS port on trunk is now using BoringSSL instead of NSS.

This affects every feature that interacts with crypto, SSL, or uses the network stack in novel ways. If you work on one, especially if it doesn't have good test coverage, please sanity check that it's still working as expected. We have shipped it on all other platforms fine, but its worth checking to be sure.

If there are any problems, please let me know.

-Steven