Enables WebRTC-TaskQueuePacer trial in tests

Bug: 1143271
Change-Id: I1b24f23d1e3749bf4a4283b38f79a607129180cf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2544547
Auto-Submit: Erik Språng <sprang@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Commit-Queue: Jesse Doherty <jwd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#828830}

testing/variations/fieldtrial_testing_config.json

@@ -7687,6 +7687,24 @@
             ]
         }
     ],
+    "WebRTC-TaskQueuePacer": [
+        {
+            "platforms": [
+                "windows",
+                "mac",
+                "chromeos",
+                "linux",
+                "ios",
+                "android",
+                "android_webview"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled"
+                }
+            ]
+        }
+    ],
     "WebRTC-VP8-Postproc-Config": [
         {
             "platforms": [