Add WebRTC-Audio-OpusMinPacketLossRate to fieldtrial_testing_config.

Bug: 896684
Change-Id: I833b99b0ae3c2162765cd8e0b16e6b729745cbba
Reviewed-on: https://chromium-review.googlesource.com/c/1304417Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603656}

testing/variations/fieldtrial_testing_config.json

@@ -5341,6 +5341,21 @@
             ]
         }
     ],
+    "WebRTC-Audio-OpusMinPacketLossRate": [
+        {
+            "platforms": [
+                "windows",
+                "mac",
+                "chromeos",
+                "linux"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled"
+                }
+            ]
+        }
+    ],
     "WebRTC-EnableWebRtcEcdsa": [
         {
             "platforms": [