Add ThrottleInstallingServiceWorker to fieldtrial_testing_config.json.

Bug: 1035448
Change-Id: Ib029e2c3115a5f0d8e9d3c9dcfd014e5851f827b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2209339Reviewed-by: Jesse Doherty <jwd@chromium.org>
Commit-Queue: Ben Kelly <wanderview@chromium.org>
Cr-Commit-Position: refs/heads/master@{#770836}

testing/variations/fieldtrial_testing_config.json

@@ -6134,6 +6134,28 @@
             ]
         }
     ],
+    "ThrottleInstallingServiceWorker": [
+        {
+            "platforms": [
+                "windows",
+                "mac",
+                "chromeos",
+                "linux",
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Emabled5_v1",
+                    "params": {
+                        "limit": "5"
+                    },
+                    "enable_features": [
+                        "ThrottleInstallingServiceWorker"
+                    ]
+                }
+            ]
+        }
+    ],
     "TopCat": [
         {
             "platforms": [