[autofill] Add fieldtrial config for AutofillDeleteDisusedData

Bug: 734151
Change-Id: Ia2a04fd5acaae8cfa32bbec102a47d31e4294db1
Reviewed-on: https://chromium-review.googlesource.com/1169422Reviewed-by: Robert Kaplow (slow) <rkaplow@chromium.org>
Commit-Queue: Roger McFarlane <rogerm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582215}

testing/variations/fieldtrial_testing_config.json

@@ -442,6 +442,27 @@
             ]
         }
     ],
+    "AutofillDeleteDisusedData": [
+        {
+            "platforms": [
+                "android",
+                "chromeos",
+                "ios",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "AutofillDeleteDisusedAddresses",
+                        "AutofillDeleteDisusedCreditCards"
+                    ]
+                }
+            ]
+        }
+    ],
     "AutofillDynamicForms": [
         {
             "platforms": [