Omnibox: Add back Steady State Elisions feature in test configs

Bug: 908440
Change-Id: Id846e2c8d209ebe77b08fa78dab90d1362e95328
Reviewed-on: https://chromium-review.googlesource.com/c/1351277Reviewed-by: Kevin Bailey <krb@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612735}

testing/variations/fieldtrial_testing_config.json

@@ -3305,6 +3305,25 @@
             ]
         }
     ],
+    "OmniboxSteadyStateElisions": [
+        {
+            "platforms": [
+                "windows",
+                "mac",
+                "chromeos",
+                "linux"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "OmniboxUIExperimentHideSteadyStateUrlScheme",
+                        "OmniboxUIExperimentHideSteadyStateUrlTrivialSubdomains"
+                    ]
+                }
+            ]
+        }
+    ],
     "OomIntervention": [
         {
             "platforms": [