Use Array<uint8_t> in DTLS1_OUTGOING_MESSAGE.

The destructor is automatic but, as a bonus, it becomes size_t-clean.
Costs us 8 more bytes of per-connection memory per outgoing message,
which isn't ideal but the previous commit saved even more, and DTLS
isn't as important as TLS in that regard.

Bug: 516
Change-Id: I69f881169088a11b9f09c4dc3577c47c4b48ce60
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/54467
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Bob Beck <bbe@google.com>

ssl/d1_both.cc

diff --git a/ssl/d1_both.cc b/ssl/d1_both.cc
index f8c04b7..3424f6e 100644
--- a/ssl/d1_both.cc
+++ b/ssl/d1_both.cc
@@ -487,10 +487,7 @@
 
 // Sending handshake messages.
 
-void DTLS_OUTGOING_MESSAGE::Clear() {
-  OPENSSL_free(data);
-  data = nullptr;
-}
+void DTLS_OUTGOING_MESSAGE::Clear() { data.Reset(); }
 
 void dtls_clear_outgoing_messages(SSL *ssl) {
   for (size_t i = 0; i < ssl->d1->outgoing_messages_len; i++) {
@@ -578,9 +575,7 @@
 
   DTLS_OUTGOING_MESSAGE *msg =
       &ssl->d1->outgoing_messages[ssl->d1->outgoing_messages_len];
-  size_t len;
-  data.Release(&msg->data, &len);
-  msg->len = len;
+  msg->data = std::move(data);
   msg->epoch = ssl->d1->w_epoch;
   msg->is_ccs = is_ccs;
 
@@ -665,7 +660,7 @@
   // DTLS messages are serialized as a single fragment in |msg|.
   CBS cbs, body;
   struct hm_header_st hdr;
-  CBS_init(&cbs, msg->data, msg->len);
+  CBS_init(&cbs, msg->data.data(), msg->data.size());
   if (!dtls1_parse_fragment(&cbs, &hdr, &body) ||
       hdr.frag_off != 0 ||
       hdr.frag_len != CBS_len(&body) ||

ssl/internal.h

diff --git a/ssl/internal.h b/ssl/internal.h
index d8df2ab..71ff0ff 100644
--- a/ssl/internal.h
+++ b/ssl/internal.h
@@ -1181,12 +1181,10 @@
   DTLS_OUTGOING_MESSAGE() {}
   DTLS_OUTGOING_MESSAGE(const DTLS_OUTGOING_MESSAGE &) = delete;
   DTLS_OUTGOING_MESSAGE &operator=(const DTLS_OUTGOING_MESSAGE &) = delete;
-  ~DTLS_OUTGOING_MESSAGE() { Clear(); }
 
   void Clear();
 
-  uint8_t *data = nullptr;
-  uint32_t len = 0;
+  Array<uint8_t> data;
   uint16_t epoch = 0;
   bool is_ccs = false;
 };