Adding field trial config for AutofillUseUniqueRendererIDsOnIOS.

Bug: 1131038, 1075444
Change-Id: Ic120ef48c37885ecc93c18a5ecbf4731240f02c7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2532559Reviewed-by: Caitlin Fischer <caitlinfischer@google.com>
Commit-Queue: Caitlin Fischer <caitlinfischer@google.com>
Cr-Commit-Position: refs/heads/master@{#826424}

testing/variations/fieldtrial_testing_config.json

@@ -1013,6 +1013,21 @@
             ]
         }
     ],
+    "AutofillUseUniqueRendererIDsOnIOS": [
+        {
+            "platforms": [
+                "ios"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "AutofillUseUniqueRendererIDsOnIOS"
+                    ]
+                }
+            ]
+        }
+    ],
     "BackForwardCache": [
         {
             "platforms": [