Revert of Disallow posting tasks to SequencedWorkerPools by default.

chrome/browser/chrome_browser_main.cc

Index: chrome/browser/chrome_browser_main.cc
diff --git a/chrome/browser/chrome_browser_main.cc b/chrome/browser/chrome_browser_main.cc
index ddae219d0d59d1b19f7bd6c7bd1df49cec96aedb..ef8d8ccada69f44a348f08479ff86379c8f99f86 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -315,12 +315,7 @@
 }
 #endif  // !defined(OS_ANDROID) && !defined(OS_CHROMEOS)
 
-// Initializes TaskScheduler if enabled via field trial or command line flag.
-// The function returns true if it enables redirection of SequencedWorkerPool to
-// TaskScheduler.
-bool MaybeInitializeTaskScheduler() {
-  bool sequenced_worker_pool_redirected = false;
-
+void MaybeInitializeTaskScheduler() {
   static constexpr char kFieldTrialName[] = "BrowserScheduler";
   std::map<std::string, std::string> variation_params;
   if (!variations::GetVariationParams(kFieldTrialName, &variation_params)) {
@@ -330,22 +325,19 @@
         << switches::kEnableBrowserTaskScheduler
         << " because there is no available variation param for this build or "
            " the task scheduler is disabled in chrome://flags.";
-    return sequenced_worker_pool_redirected;
+    return;
   }
 
   if (!task_scheduler_util::InitializeDefaultTaskScheduler(variation_params))
-    return sequenced_worker_pool_redirected;
+    return;
 
   // TODO(gab): Remove this when http://crbug.com/622400 concludes.
   const auto sequenced_worker_pool_param =
       variation_params.find("RedirectSequencedWorkerPools");
   if (sequenced_worker_pool_param != variation_params.end() &&
       sequenced_worker_pool_param->second == "true") {
-    sequenced_worker_pool_redirected = true;
-    base::SequencedWorkerPool::EnableWithRedirectionToTaskSchedulerForProcess();
-  }
-
-  return sequenced_worker_pool_redirected;
+    base::SequencedWorkerPool::RedirectToTaskSchedulerForProcess();
+  }
 }
 
 // Returns the new local state object, guaranteed non-NULL.
@@ -1245,8 +1237,7 @@
   // IOThread's initialization which happens in BrowserProcess:PreCreateThreads.
   SetupFieldTrials();
 
-  // Initializing TaskScheduler and enabling SequencedWorkerPool needs to be
-  // here for the following reasons:
+  // Task Scheduler initialization needs to be here for the following reasons:
   //   * After |SetupFieldTrials()|: Initialization uses variations.
   //   * Before |SetupMetrics()|: |SetupMetrics()| uses the blocking pool. The
   //         Task Scheduler must do any necessary redirection before then.
@@ -1255,14 +1246,7 @@
   //         threads itself so instantiating it earlier is also incorrect.
   // To maintain scoping symmetry, if this line is moved, the corresponding
   // shutdown call may also need to be moved.
-  const bool sequenced_worker_pool_redirected = MaybeInitializeTaskScheduler();
-
-  // If MaybeInitializeTaskScheduler() hasn't enabled SequencedWorkerPool with
-  // redirection to TaskScheduler, enable it without redirection.
-  // TODO(fdoray): Remove this once the SequencedWorkerPool to TaskScheduler
-  // redirection experiment concludes https://crbug.com/622400.
-  if (!sequenced_worker_pool_redirected)
-    base::SequencedWorkerPool::EnableForProcess();
+  MaybeInitializeTaskScheduler();
 
   SetupMetrics();