Make requesting SDES available only on Fuchsia builds

Bug: webrtc:11066
Change-Id: I0707cf63064830a55db31e883dc7b15aa675950b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/257900
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36438}
diff --git a/pc/peer_connection.cc b/pc/peer_connection.cc
index e5a83b0..1a17fd4 100644
--- a/pc/peer_connection.cc
+++ b/pc/peer_connection.cc
@@ -280,8 +280,12 @@
   bool default_enabled =
       (dependencies.cert_generator || !configuration.certificates.empty());
 
+#if defined(WEBRTC_FUCHSIA)
   // The `configuration` can override the default value.
   return configuration.enable_dtls_srtp.value_or(default_enabled);
+#else
+  return default_enabled;
+#endif
 }
 
 }  // namespace
@@ -303,7 +307,9 @@
     bool disable_link_local_networks;
     absl::optional<int> screencast_min_bitrate;
     absl::optional<bool> combined_audio_video_bwe;
+#if defined(WEBRTC_FUCHSIA)
     absl::optional<bool> enable_dtls_srtp;
+#endif
     TcpCandidatePolicy tcp_candidate_policy;
     CandidateNetworkPolicy candidate_network_policy;
     int audio_jitter_buffer_max_packets;
@@ -372,7 +378,9 @@
          disable_link_local_networks == o.disable_link_local_networks &&
          screencast_min_bitrate == o.screencast_min_bitrate &&
          combined_audio_video_bwe == o.combined_audio_video_bwe &&
+#if defined(WEBRTC_FUCHSIA)
          enable_dtls_srtp == o.enable_dtls_srtp &&
+#endif
          ice_candidate_pool_size == o.ice_candidate_pool_size &&
          prune_turn_ports == o.prune_turn_ports &&
          turn_port_prune_policy == o.turn_port_prune_policy &&