Add common TLS extensions

Bug: webrtc:8019
Change-Id: Ic60e892f0acbe394472319c4d943690828446610
Reviewed-on: https://chromium-review.googlesource.com/580261
Commit-Queue: Emad Omara <emadomara@webrtc.org>
Reviewed-by: Justin Uberti <juberti@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#19106}

webrtc/rtc_base/openssladapter.cc

@@ -365,6 +365,11 @@ OpenSSLAdapter::BeginSSL() {
     SSL_set_tlsext_host_name(ssl_, ssl_host_name_.c_str());
   }
 
+  // Set a couple common TLS extensions; even though we don't use them yet.
+  // TODO(emadomara) Add ALPN extension.
+  SSL_enable_ocsp_stapling(ssl_);
+  SSL_enable_signed_cert_timestamps(ssl_);
+
   // the SSL object owns the bio now
   bio = nullptr;