diff --git a/dom/webidl/PeerConnectionImpl.webidl b/dom/webidl/PeerConnectionImpl.webidl
index bd5719a5ee32..e87445a1073b 100644
--- a/dom/webidl/PeerConnectionImpl.webidl
+++ b/dom/webidl/PeerConnectionImpl.webidl
@@ -53,6 +53,10 @@ interface PeerConnectionImpl  {
                   optional unsigned long interToneGap = 70);
   [Throws]
   DOMString getDTMFToneBuffer(RTCRtpSender sender);
+  sequence<RTCRtpSourceEntry> getRtpSources(MediaStreamTrack track,
+                                            DOMHighResTimeStamp rtpSourceNow);
+  DOMHighResTimeStamp getNowInRtpSourceReferenceTime();
+
   [Throws]
   void replaceTrackNoRenegotiation(TransceiverImpl transceiverImpl,
                                    MediaStreamTrack? withTrack);
@@ -62,6 +66,13 @@ interface PeerConnectionImpl  {
   void addRIDExtension(MediaStreamTrack recvTrack, unsigned short extensionId);
   void addRIDFilter(MediaStreamTrack recvTrack, DOMString rid);
 
+  // Inserts CSRC data for the RtpSourceObserver for testing
+  void insertAudioLevelForContributingSource(MediaStreamTrack recvTrack,
+                                             unsigned long source,
+                                             DOMHighResTimeStamp timestamp,
+                                             boolean hasLevel,
+                                             byte level);
+
   void enablePacketDump(unsigned long level,
                         mozPacketDumpType type,
                         boolean sending);
diff --git a/dom/webidl/RTCPeerConnection.webidl b/dom/webidl/RTCPeerConnection.webidl
index d04f23ad9331..c907e6cb43cc 100644
--- a/dom/webidl/RTCPeerConnection.webidl
+++ b/dom/webidl/RTCPeerConnection.webidl
@@ -135,6 +135,16 @@ interface RTCPeerConnection : EventTarget  {
   sequence<RTCRtpReceiver> getReceivers();
   sequence<RTCRtpTransceiver> getTransceivers();
 
+  // test-only: for testing getContributingSources
+  [ChromeOnly]
+  DOMHighResTimeStamp mozGetNowInRtpSourceReferenceTime();
+  // test-only: for testing getContributingSources
+  [ChromeOnly]
+  void mozInsertAudioLevelForContributingSource(RTCRtpReceiver receiver,
+                                                unsigned long source,
+                                                DOMHighResTimeStamp timestamp,
+                                                boolean hasLevel,
+                                                byte level);
   [ChromeOnly]
   void mozAddRIDExtension(RTCRtpReceiver receiver, unsigned short extensionId);
   [ChromeOnly]