New class RtxReceiveStream.

BUG=webrtc:7135

Review-Url: https://codereview.webrtc.org/2888093002
Cr-Original-Commit-Position: refs/heads/master@{#18212}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: eed52bff8d3e2d83207da624ec0a8f6441f1c98f
diff --git a/call/BUILD.gn b/call/BUILD.gn
index 0d87b2f..7728104 100644
--- a/call/BUILD.gn
+++ b/call/BUILD.gn
@@ -42,6 +42,8 @@
     "rtp_demuxer.cc",
     "rtp_transport_controller_send.cc",
     "rtp_transport_controller_send.h",
+    "rtx_receive_stream.cc",
+    "rtx_receive_stream.h",
   ]
 
   if (!build_with_chromium && is_clang) {
@@ -87,6 +89,7 @@
       "bitrate_estimator_tests.cc",
       "call_unittest.cc",
       "flexfec_receive_stream_unittest.cc",
+      "rtx_receive_stream_unittest.cc",
     ]
     deps = [
       ":call",