Use accessors to reach into ASN1_STRING

This does the same thing, just is a bit more future-proof for when
BoringSSL and OpenSSL make the type opaque in the future.

Bug: chromium:443769299
Change-Id: I4a74db8ef58bbd464e6a6a46b31b20aada746432
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/462700
Auto-Submit: David Benjamin <davidben@google.com>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#48024}

rtc_base/boringssl_certificate.cc

diff --git a/rtc_base/boringssl_certificate.cc b/rtc_base/boringssl_certificate.cc
index a4f919f..e7ceca3 100644
--- a/rtc_base/boringssl_certificate.cc
+++ b/rtc_base/boringssl_certificate.cc
@@ -157,7 +157,7 @@
   }
 
   unsigned tag;
-  switch (asn1_time->type) {
+  switch (ASN1_STRING_type(asn1_time.get())) {
     case V_ASN1_UTCTIME:
       tag = CBS_ASN1_UTCTIME;
       break;
@@ -170,7 +170,8 @@
 
   CBB child;
   if (!CBB_add_asn1(cbb, &child, tag) ||
-      !CBB_add_bytes(&child, asn1_time->data, asn1_time->length) ||
+      !CBB_add_bytes(&child, ASN1_STRING_get0_data(asn1_time.get()),
+                     ASN1_STRING_length(asn1_time.get())) ||
       !CBB_flush(cbb)) {
     return false;
   }