Prepare OneGroupPerRenderer experiment for beta

Bug: b:172213843
Change-Id: Id30e9144356bd6241f85812387892956bcf311a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3914006
Reviewed-by: Erik Chen <erikchen@chromium.org>
Commit-Queue: Youssef Esmat <youssefesmat@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1050649}

testing/variations/fieldtrial_testing_config.json

@@ -7248,6 +7248,21 @@
             ]
         }
     ],
+    "OneGroupPerRenderer": [
+        {
+            "platforms": [
+                "chromeos"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "OneGroupPerRenderer"
+                    ]
+                }
+            ]
+        }
+    ],
     "OneTimeGeolocationPermission": [
         {
             "platforms": [