Implement dual stream full stack test and loopback tool

Bug: webrtc:8588
Change-Id: I0abec4891a723c98001f4580f0cfa57a5d6d6bdb
Reviewed-on: https://webrtc-review.googlesource.com/34441
Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21416}
diff --git a/BUILD.gn b/BUILD.gn
index 9b4248b..b492f57 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -59,6 +59,7 @@
         "system_wrappers:system_wrappers_unittests",
         "test",
         "video:screenshare_loopback",
+        "video:sv_loopback",
         "video:video_loopback",
         "voice_engine:voice_engine_unittests",
       ]