Field trial testing config for etld+1 in network isolation key

Bug: 1018718
Change-Id: I1f43af0d604d58abe37f2cacf58283b795e1d725
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1948230
Commit-Queue: Shivani Sharma <shivanisha@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726028}

testing/variations/fieldtrial_testing_config.json

@@ -7015,6 +7015,26 @@
             ]
         }
     ],
+    "UseRegistrableDomainInNetworkIsolationKey": [
+        {
+            "platforms": [
+                "android",
+                "android_webview",
+                "chromeos",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "UseRegistrableDomainInNetworkIsolationKey"
+                    ]
+                }
+            ]
+        }
+    ],
     "UseSkiaRenderer": [
         {
             "platforms": [