Update API for Objective-C RTCAudioTrack and RTCVideoTrack.

webrtc/api/BUILD.gn

Index: webrtc/api/BUILD.gn
diff --git a/webrtc/api/BUILD.gn b/webrtc/api/BUILD.gn
index 0d88774927c9a3d3fef081d45f08f91165e9f1f5..f70445a5cd3e4e401e1fcea37e776ff5d33e14ac 100644
--- a/webrtc/api/BUILD.gn
+++ b/webrtc/api/BUILD.gn
@@ -19,6 +19,10 @@ if (is_ios) {
       "-Wobjc-missing-property-synthesis",
     ]
     sources = [
+      "objc/RTCAudioTrack+Private.h",
+      "objc/RTCAudioTrack.h",
+      "objc/RTCAudioTrack.mm",
+
       # Add these when there's a BUILD.gn for peer connection APIs
       #"objc/RTCIceCandidate+Private.h",
       #"objc/RTCIceCandidate.h",
@@ -29,6 +33,9 @@ if (is_ios) {
       "objc/RTCIceServer+Private.h",
       "objc/RTCIceServer.h",
       "objc/RTCIceServer.mm",
+      "objc/RTCVideoTrack+Private.h",
+      "objc/RTCVideoTrack.h",
+      "objc/RTCVideoTrack.mm",
       "objc/WebRTC-Prefix.pch",
     ]
   }