[AF] Adding Fieldtrial Config For Autocomplete Retention Policy

Change-Id: Ide05b93e62e29bcf34e813022b1214f37af1c0be
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1498783Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Sebastien Lalancette <seblalancette@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638613}

testing/variations/fieldtrial_testing_config.json

@@ -551,6 +551,26 @@
             ]
         }
     ],
+    "AutocompleteRetentionPolicy": [
+        {
+            "platforms": [
+                "android",
+                "chromeos",
+                "ios",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "AutocompleteRetentionPolicyEnabled"
+                    ]
+                }
+            ]
+        }
+    ],
     "AutofillDropdownLayout": [
         {
             "platforms": [