Deprecate RtpTransceiver.setDirection()

This is part of the work to add a return value to the function.

Bug: chromium:980879
Change-Id: Ifa5e491a6b493a927da9783f23bf9f44be81aa8a
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/181863
Reviewed-by: Guido Urdaneta <guidou@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31950}
diff --git a/api/rtp_transceiver_interface.h b/api/rtp_transceiver_interface.h
index cdda34b..fd3555f 100644
--- a/api/rtp_transceiver_interface.h
+++ b/api/rtp_transceiver_interface.h
@@ -111,7 +111,8 @@
   // https://w3c.github.io/webrtc-pc/#dom-rtcrtptransceiver-direction
   // TODO(hta): Deprecate SetDirection without error and rename
   // SetDirectionWithError to SetDirection, remove default implementations.
-  virtual void SetDirection(RtpTransceiverDirection new_direction);
+  RTC_DEPRECATED virtual void SetDirection(
+      RtpTransceiverDirection new_direction);
   virtual RTCError SetDirectionWithError(RtpTransceiverDirection new_direction);
 
   // The current_direction attribute indicates the current direction negotiated