Add periodic logging of video stats.

webrtc/video/send_statistics_proxy_unittest.cc

Index: webrtc/video/send_statistics_proxy_unittest.cc
diff --git a/webrtc/video/send_statistics_proxy_unittest.cc b/webrtc/video/send_statistics_proxy_unittest.cc
index ad51f2abe69111a875f9a91d3c8f7214d418f101..101c4422e042dd3eff12c462dc7b85f9eac53516 100644
--- a/webrtc/video/send_statistics_proxy_unittest.cc
+++ b/webrtc/video/send_statistics_proxy_unittest.cc
@@ -45,6 +45,10 @@ class SendStatisticsProxyTest : public ::testing::Test {
         &fake_clock_, GetTestConfig(),
         VideoEncoderConfig::ContentType::kRealtimeVideo));
     expected_ = VideoSendStream::Stats();
+    for (const auto& ssrc : config_.rtp.ssrcs)
+      expected_.substreams[ssrc].is_rtx = false;
+    for (const auto& ssrc : config_.rtp.rtx.ssrcs)
+      expected_.substreams[ssrc].is_rtx = true;
   }
 
   VideoSendStream::Config GetTestConfig() {
@@ -73,6 +77,7 @@ class SendStatisticsProxyTest : public ::testing::Test {
       const VideoSendStream::StreamStats& a = it->second;
       const VideoSendStream::StreamStats& b = corresponding_it->second;
 
+      EXPECT_EQ(a.is_rtx, b.is_rtx);
       EXPECT_EQ(a.frame_counts.key_frames, b.frame_counts.key_frames);
       EXPECT_EQ(a.frame_counts.delta_frames, b.frame_counts.delta_frames);
       EXPECT_EQ(a.total_bitrate_bps, b.total_bitrate_bps);