Add screenshare perf tests with lossy links

This is a re-land of https://codereview.webrtc.org/1409513005/
Fingers crossed, the problems previously seen have been resolved by
https://codereview.webrtc.org/1412233003/

BUG=

Review URL: https://codereview.webrtc.org/1409993011

Cr-Commit-Position: refs/heads/master@{#10751}
diff --git a/webrtc/video/full_stack.cc b/webrtc/video/full_stack.cc
index 8fdccfd..e870c1f 100644
--- a/webrtc/video/full_stack.cc
+++ b/webrtc/video/full_stack.cc
@@ -145,6 +145,30 @@
   RunTest(config);
 }
 
+TEST_F(FullStackTest, ScreenshareSlidesVP8_2TL_LossyNet) {
+  VideoQualityTest::Params screenshare = {
+      {1850, 1110, 5, 50000, 200000, 2000000, "VP8", 2, 1, 400000},
+      {},          // Video-specific.
+      {true, 10},  // Screenshare-specific.
+      {"screenshare_slides_lossy_net", 0.0, 0.0, kFullStackTestDurationSecs}};
+  screenshare.pipe.loss_percent = 5;
+  screenshare.pipe.queue_delay_ms = 200;
+  screenshare.pipe.link_capacity_kbps = 500;
+  RunTest(screenshare);
+}
+
+TEST_F(FullStackTest, ScreenshareSlidesVP8_2TL_VeryLossyNet) {
+  VideoQualityTest::Params screenshare = {
+      {1850, 1110, 5, 50000, 200000, 2000000, "VP8", 2, 1, 400000},
+      {},          // Video-specific.
+      {true, 10},  // Screenshare-specific.
+      {"screenshare_slides_very_lossy", 0.0, 0.0, kFullStackTestDurationSecs}};
+  screenshare.pipe.loss_percent = 10;
+  screenshare.pipe.queue_delay_ms = 200;
+  screenshare.pipe.link_capacity_kbps = 500;
+  RunTest(screenshare);
+}
+
 TEST_F(FullStackTest, ScreenshareSlidesVP9_2SL) {
   VideoQualityTest::Params screenshare = {
       {1850, 1110, 5, 50000, 200000, 2000000, "VP9", 1, 0, 400000},
diff --git a/webrtc/video/video_quality_test.cc b/webrtc/video/video_quality_test.cc
index a46fe1b..878beed 100644
--- a/webrtc/video/video_quality_test.cc
+++ b/webrtc/video/video_quality_test.cc
@@ -641,9 +641,10 @@
     // use that feature with pack loss, since the NACK request would end up
     // retransmitting the wrong packets.
     RTC_CHECK(params_.ss.selected_sl == -1 ||
-              params_.ss.num_spatial_layers == 1);
+              params_.ss.selected_sl == params_.ss.num_spatial_layers - 1);
     RTC_CHECK(params_.common.selected_tl == -1 ||
-              params_.common.num_temporal_layers == 1);
+              params_.common.selected_tl ==
+                  params_.common.num_temporal_layers - 1);
   }
 
   // TODO(ivica): Should max_bitrate_bps == -1 represent inf max bitrate, as it