Field trial testing config for split cache

Bug: 910708
Change-Id: Ib2702d8600c5c14e2d7290a61eaeb0687b7422b7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2441113Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Shivani Sharma <shivanisha@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812298}

testing/variations/fieldtrial_testing_config.json

@@ -6420,10 +6420,11 @@
             ],
             "experiments": [
                 {
-                    "name": "Enabled_Stable",
+                    "name": "Experiment_Triple_Key_20201001",
                     "enable_features": [
                         "AppendFrameOriginToNetworkIsolationKey",
-                        "SplitCacheByNetworkIsolationKey"
+                        "SplitCacheByNetworkIsolationKey",
+                        "UseRegistrableDomainInNetworkIsolationKey"
                     ]
                 }
             ]