Add a TaskPriority cap to the SWP redirection to experiment with no redirections at USER_BLOCKING.

components/task_scheduler_util/variations/browser_variations_util.cc

Index: components/task_scheduler_util/variations/browser_variations_util.cc
diff --git a/components/task_scheduler_util/variations/browser_variations_util.cc b/components/task_scheduler_util/variations/browser_variations_util.cc
index a3616b10bc492b21eaf76d5df8a26035f9e7a12f..29f2e32f8a4bfc3be5bc2ac48abb02ec1399daa3 100644
--- a/components/task_scheduler_util/variations/browser_variations_util.cc
+++ b/components/task_scheduler_util/variations/browser_variations_util.cc
@@ -136,7 +136,20 @@ void MaybePerformBrowserTaskSchedulerRedirection() {
           switches::kDisableBrowserTaskScheduler) &&
       sequenced_worker_pool_param != variation_params.end() &&
       sequenced_worker_pool_param->second == "true") {
-    base::SequencedWorkerPool::EnableWithRedirectionToTaskSchedulerForProcess();
+    // Check a variation that allows capping all redirections at USER_VISIBLE
+    // (no USER_BLOCKING) to observe the side-effects of multiple priority
+    // levels in the foreground IO pool.
+    const auto sequenced_worker_pool_cap_priority_param =
+        variation_params.find("CapSequencedWorkerPoolsAtUserVisible");
+
+    const base::TaskPriority max_task_priority =
+        sequenced_worker_pool_cap_priority_param != variation_params.end() &&
+        sequenced_worker_pool_cap_priority_param->second == "true"
+            ? base::TaskPriority::USER_VISIBLE
+            : base::TaskPriority::HIGHEST;
+
+    base::SequencedWorkerPool::EnableWithRedirectionToTaskSchedulerForProcess(
+        max_task_priority);
   } else {
     base::SequencedWorkerPool::EnableForProcess();
   }