external/boringssl: Sync to f11ea19043f2b3ee42e4a76d0645914347e1a36e.

This includes the following changes:

https://boringssl.googlesource.com/boringssl/+log/ba9da449a4bf5b90cd020807f2c4176e3ab6fe3e..f11ea19043f2b3ee42e4a76d0645914347e1a36e

Test: BoringSSL CTS Presubmits.
Change-Id: Ifb6e46262349afd7cd7a23d59a684e25fb723208
diff --git a/src/ssl/ssl_lib.cc b/src/ssl/ssl_lib.cc
index ef79831..6312504 100644
--- a/src/ssl/ssl_lib.cc
+++ b/src/ssl/ssl_lib.cc
@@ -1274,6 +1274,9 @@
     case SSL_HANDOFF:
       return SSL_ERROR_HANDOFF;
 
+    case SSL_HANDBACK:
+      return SSL_ERROR_HANDBACK;
+
     case SSL_READING: {
       BIO *bio = SSL_get_rbio(ssl);
       if (BIO_should_read(bio)) {