[AdTagging] Enable AdTagging field trial on bots

Bug: 877148
Change-Id: I757fa7363dd11f4c2db534fc7dbc3b46174a623f
Reviewed-on: https://chromium-review.googlesource.com/1188602Reviewed-by: Robert Kaplow (slow) <rkaplow@chromium.org>
Commit-Queue: Josh Karlin <jkarlin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585900}

testing/variations/fieldtrial_testing_config.json

@@ -38,6 +38,25 @@
             ]
         }
     ],
+    "AdTagging": [
+        {
+            "platforms": [
+                "android",
+                "chromeos",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "AdTagging"
+                    ]
+                }
+            ]
+        }
+    ],
     "AllowClientHintsToThirdParty": [
         {
             "platforms": [