Updating fieldtrial testing config for TabPersistentStoreTaskRunner

Bug: 957737
Change-Id: I0ad87488e64b0e233a8fdc16399947b6c1362897
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1697313
Auto-Submit: Sam Maier <smaier@chromium.org>
Commit-Queue: Jesse Doherty <jwd@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#678005}

testing/variations/fieldtrial_testing_config.json

@@ -5220,6 +5220,21 @@
             ]
         }
     ],
+    "TabPersistentStoreTaskRunner": [
+        {
+            "platforms": [
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "TabPersistentStoreTaskRunner"
+                    ]
+                }
+            ]
+        }
+    ],
     "TabRanker": [
         {
             "platforms": [