Add WebRTC-CongestionWindow field trial config

Bug: 952831
Change-Id: I12800e6db741632617af859a7852565e6da99d08
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1599624Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Evan Shrubsole <eshr@google.com>
Cr-Commit-Position: refs/heads/master@{#658482}

testing/variations/fieldtrial_testing_config.json

@@ -5881,6 +5881,24 @@
             ]
         }
     ],
+    "WebRTC-CongestionWindow": [
+        {
+            "platforms": [
+                "windows",
+                "mac",
+                "chromeos",
+                "linux",
+                "ios",
+                "android",
+                "android_webview"
+            ],
+            "experiments": [
+                {
+                    "name": "QueueSize:800,MinBitrate:30000"
+                }
+            ]
+        }
+    ],
     "WebRTC-EnableWebRtcEcdsa": [
         {
             "platforms": [