Redirect HistoryService thread to TaskScheduler via a field trial.

testing/variations/fieldtrial_testing_config.json

 {
     "AndroidSessionNotifications": [
         {
             "platforms": [
                 "android"
             ],
             "experiments": [
                 {
                     "name": "Disabled"
                 }
@@ skipping 200 matching lines @@
                 "win"
             ],
             "experiments": [
                 {
                     "name": "Enabled",
                     "params": {
                         "Background": "3;8;0.1;0;30000",
                         "BackgroundFileIO": "3;8;0.1;0;30000",
                         "Foreground": "8;32;0.3;0;30000",
                         "ForegroundFileIO": "8;32;0.3;0;30000",
+                        "RedirectHistoryService": "true",
                         "RedirectSequencedWorkerPools": "true"
                     }
                 },
                 {
                     "name": "EnableViaFlag",
                     "forcing_flag": "enable-browser-task-scheduler",
                     "params": {
                         "Background": "3;8;0.1;0;30000",
                         "BackgroundFileIO": "3;8;0.1;0;30000",
                         "Foreground": "8;32;0.3;0;30000",
                         "ForegroundFileIO": "8;32;0.3;0;30000",
+                        "RedirectHistoryService": "true",
                         "RedirectSequencedWorkerPools": "true"
                     }
                 },
                 {
                     "name": "DisableViaFlag",
                     "forcing_flag": "disable-browser-task-scheduler"
                 }
             ]
         }
     ],
@@ skipping 2119 matching lines @@
                 {
                     "name": "Enabled",
                     "enable_features": [
                         "use-new-media-cache"
                     ]
                 }
             ]
         }
     ]
 }