Add field trial config for the NewExtensionUpdaterService feature.

Bug: 828615, 722942
Change-Id: I75766fc9cf91bc0a49e38abdd3dce1e3b1627b85
Reviewed-on: https://chromium-review.googlesource.com/1008830Reviewed-by: Robert Kaplow (slow) <rkaplow@chromium.org>
Commit-Queue: Minh Nguyen <mxnguyen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581240}

testing/variations/fieldtrial_testing_config.json

@@ -2505,6 +2505,24 @@
             ]
         }
     ],
+    "NewExtensionUpdaterService": [
+        {
+            "platforms": [
+                "chromeos",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "NewExtensionUpdaterService"
+                    ]
+                }
+            ]
+        }
+    ],
     "NewPrintPreview": [
         {
             "platforms": [