Only resolve which cipher list to use once.

Get some of the duplicate logic out of the way.

Change-Id: Iee7c64577e14d1ddfead7e1e32c42c5c9f2a310d
Reviewed-on: https://boringssl-review.googlesource.com/11981
Reviewed-by: Steven Valdez <svaldez@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

ssl/ssl_lib.c

diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index 491c408..b8d4549 100644
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -1564,23 +1564,13 @@
     return NULL;
   }
 
-  if (ssl->cipher_list != NULL) {
-    return ssl->cipher_list->ciphers;
+  const struct ssl_cipher_preference_list_st *prefs =
+      ssl_get_cipher_preferences(ssl);
+  if (prefs == NULL) {
+    return NULL;
   }
 
-  if (ssl->version >= TLS1_1_VERSION && ssl->ctx->cipher_list_tls11 != NULL) {
-    return ssl->ctx->cipher_list_tls11->ciphers;
-  }
-
-  if (ssl->version >= TLS1_VERSION && ssl->ctx->cipher_list_tls10 != NULL) {
-    return ssl->ctx->cipher_list_tls10->ciphers;
-  }
-
-  if (ssl->ctx->cipher_list != NULL) {
-    return ssl->ctx->cipher_list->ciphers;
-  }
-
-  return NULL;
+  return prefs->ciphers;
 }
 
 /* return a STACK of the ciphers available for the SSL and in order of