Enable IdentityDisc in fieldtrial_testing_config

The feature is tracked in crbug.com/955951. It is rolled out to
dev/canary/beta.

R=isherman@chromium.org

Change-Id: I4f5c3c02b0dc088977e77561fbd29216b904939c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1726819Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Pavel Yatsuk <pavely@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682560}

testing/variations/fieldtrial_testing_config.json

@@ -155,6 +155,21 @@
             ]
         }
     ],
+    "AndroidIdentityDisc": [
+        {
+            "platforms": [
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "IdentityDisc"
+                    ]
+                }
+            ]
+        }
+    ],
     "AndroidInProductHelpContextualSearchPromotePanelOpen": [
         {
             "platforms": [