Only use BoringSSL time callback in unit tests.

webrtc/base/sslstreamadapter.cc

Index: webrtc/base/sslstreamadapter.cc
diff --git a/webrtc/base/sslstreamadapter.cc b/webrtc/base/sslstreamadapter.cc
index 17e758e8116dfa706a514fa9b80bc125b586d12d..c3ef3bc3aefa5e39ab4792f7d3f767a972cb8dcb 100644
--- a/webrtc/base/sslstreamadapter.cc
+++ b/webrtc/base/sslstreamadapter.cc
@@ -160,6 +160,9 @@ bool SSLStreamAdapter::IsAcceptableCipher(const std::string& cipher,
 std::string SSLStreamAdapter::SslCipherSuiteToName(int cipher_suite) {
   return OpenSSLStreamAdapter::SslCipherSuiteToName(cipher_suite);
 }
+void SSLStreamAdapter::enable_time_callback_for_testing() {
+  OpenSSLStreamAdapter::enable_time_callback_for_testing();
+}
 #endif  // SSL_USE_OPENSSL
 
 ///////////////////////////////////////////////////////////////////////////////