Add test config for ServiceWorkerStartupOptimizations.

For more test coverage.

Bug: 561209
Change-Id: Ibcd2c1b854d4748fb948998da9def1279e6daded
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1911343
Commit-Queue: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715422}

testing/variations/fieldtrial_testing_config.json

@@ -3865,26 +3865,6 @@
             ]
         }
     ],
-    "OffMainThreadServiceWorkerStartup": [
-        {
-            "platforms": [
-                "android",
-                "android_webview",
-                "chromeos",
-                "linux",
-                "mac",
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled",
-                    "enable_features": [
-                        "OffMainThreadServiceWorkerStartup"
-                    ]
-                }
-            ]
-        }
-    ],
     "OfferUploadCreditCards": [
         {
             "platforms": [
@@ -5869,7 +5849,7 @@
             ]
         }
     ],
-    "ServiceWorkerOnUI": [
+    "ServiceWorkerStartupOptimizations": [
         {
             "platforms": [
                 "android",
@@ -5881,9 +5861,11 @@
             ],
             "experiments": [
                 {
-                    "name": "Enabled",
+                    "name": "Enabled_All",
                     "enable_features": [
-                        "ServiceWorkerOnUI"
+                        "OffMainThreadServiceWorkerStartup",
+                        "ServiceWorkerOnUI",
+                        "ServiceWorkerPrefersUnusedProcess"
                     ]
                 }
             ]