Add a clock to be used for getting the NTP time in RtcpTransceiverConfig.

Note: google3 needs to set this clock before we can start using it.

Bug: webrtc:11327
Change-Id: I0436c6633976afe208f28601fdfd50e0f6f54d6e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/214480
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Paul Hallak <phallak@google.com>
Cr-Commit-Position: refs/heads/master@{#33653}
diff --git a/modules/rtp_rtcp/source/rtcp_transceiver_config.h b/modules/rtp_rtcp/source/rtcp_transceiver_config.h
index 8a8fd6a..0501b9a 100644
--- a/modules/rtp_rtcp/source/rtcp_transceiver_config.h
+++ b/modules/rtp_rtcp/source/rtcp_transceiver_config.h
@@ -17,6 +17,7 @@
 #include "api/task_queue/task_queue_base.h"
 #include "api/video/video_bitrate_allocation.h"
 #include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
+#include "system_wrappers/include/clock.h"
 #include "system_wrappers/include/ntp_time.h"
 
 namespace webrtc {
@@ -61,6 +62,9 @@
   // Maximum packet size outgoing transport accepts.
   size_t max_packet_size = 1200;
 
+  // The clock to use when querying for the NTP time. Should be set.
+  Clock* clock = nullptr;
+
   // Transport to send rtcp packets to. Should be set.
   Transport* outgoing_transport = nullptr;