Store video_quality_loopback_test perf results in Chart JSON format.

Adds a flag to store the perf results in a JSON file using the Chart
JSON format [1].

[1] https://github.com/catapult-project/catapult/blob/master/dashboard/docs/data-format.md

TBR=phoglund@webrtc.org

Bug: chromium:755660
Change-Id: I6a896654a4a558df217ddefa4e8a52a487cdbebd
Reviewed-on: https://webrtc-review.googlesource.com/43180
Commit-Queue: Edward Lemur <ehmaldonado@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21809}
diff --git a/rtc_tools/BUILD.gn b/rtc_tools/BUILD.gn
index 0b1c631..976fa06 100644
--- a/rtc_tools/BUILD.gn
+++ b/rtc_tools/BUILD.gn
@@ -66,6 +66,7 @@
   ]
   deps = [
     "../common_video",
+    "../test:perf_test",
     "//third_party/libyuv",
   ]
 }
@@ -79,6 +80,7 @@
   deps = [
     ":command_line_parser",
     ":video_quality_analysis",
+    "../test:perf_test",
     "//build/win:default_exe_manifest",
   ]
 }