[reference - do not submit] Always create four pools in TaskSchedulerImpl.

components/task_scheduler_util/browser/initialization.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/task_scheduler_util/browser/initialization.h"
 
 #include <map>
 #include <string>
 
 #include "base/command_line.h"
-#include "base/logging.h"
-#include "base/task_scheduler/scheduler_worker_params.h"
+#include "base/memory/ptr_util.h"
 #include "base/task_scheduler/switches.h"
-#include "base/task_scheduler/task_traits.h"
-#include "base/threading/platform_thread.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "components/task_scheduler_util/common/variations_util.h"
 #include "components/variations/variations_associated_data.h"
 
 namespace task_scheduler_util {
 
 namespace {
 
 constexpr char kFieldTrialName[] = "BrowserScheduler";
 
-enum WorkerPoolType : size_t {
-  BACKGROUND = 0,
-  BACKGROUND_BLOCKING,
-  FOREGROUND,
-  FOREGROUND_BLOCKING,
-  WORKER_POOL_COUNT  // Always last.
-};
-
 }  // namespace
 
-std::vector<base::SchedulerWorkerPoolParams>
-GetBrowserWorkerPoolParamsFromVariations() {
-  using ThreadPriority = base::ThreadPriority;
-
+std::unique_ptr<base::TaskSchedulerInitParams>
+GetBrowserTaskSchedulerInitParamsFromVariations() {
   std::map<std::string, std::string> variation_params;
   if (!::variations::GetVariationParams(kFieldTrialName, &variation_params))
-    return std::vector<base::SchedulerWorkerPoolParams>();
+    return nullptr;
 
-  std::vector<SchedulerImmutableWorkerPoolParams> immutable_worker_pool_params;
-  DCHECK_EQ(BACKGROUND, immutable_worker_pool_params.size());
-  immutable_worker_pool_params.emplace_back("Background",
-                                            ThreadPriority::BACKGROUND);
-  DCHECK_EQ(BACKGROUND_BLOCKING, immutable_worker_pool_params.size());
-  immutable_worker_pool_params.emplace_back("BackgroundBlocking",
-                                            ThreadPriority::BACKGROUND);
-  DCHECK_EQ(FOREGROUND, immutable_worker_pool_params.size());
-  immutable_worker_pool_params.emplace_back("Foreground",
-                                            ThreadPriority::NORMAL);
-  // Tasks posted to SequencedWorkerPool or BrowserThreadImpl may be redirected
-  // to this pool. Since COM STA is initialized in these environments, it must
-  // also be initialized in this pool.
-  DCHECK_EQ(FOREGROUND_BLOCKING, immutable_worker_pool_params.size());
-  immutable_worker_pool_params.emplace_back(
-      "ForegroundBlocking", ThreadPriority::NORMAL,
-      base::SchedulerBackwardCompatibility::INIT_COM_STA);
+  auto init_params = base::MakeUnique<base::TaskSchedulerInitParams>(
+      StringToVariableWorkerPoolParams(variation_params["Background"]),
+      StringToVariableWorkerPoolParams(variation_params["BackgroundBlocking"]),
+      StringToVariableWorkerPoolParams(variation_params["Foreground"]),
+      StringToVariableWorkerPoolParams(variation_params["ForegroundBlocking"]));
 
-  return GetWorkerPoolParams(immutable_worker_pool_params, variation_params);
-}
+  if (init_params->IsValid())
+    return init_params;
 
-size_t BrowserWorkerPoolIndexForTraits(const base::TaskTraits& traits) {
-  const bool is_background =
-      traits.priority() == base::TaskPriority::BACKGROUND;
-  if (traits.may_block() || traits.with_base_sync_primitives())
-    return is_background ? BACKGROUND_BLOCKING : FOREGROUND_BLOCKING;
-  return is_background ? BACKGROUND : FOREGROUND;
+  return nullptr;
 }
 
 void MaybePerformBrowserTaskSchedulerRedirection() {
   // TODO(gab): Remove this when http://crbug.com/622400 concludes.
   if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kDisableBrowserTaskScheduler) &&
       variations::GetVariationParamValue(
           kFieldTrialName, "RedirectSequencedWorkerPools") == "true") {
     const base::TaskPriority max_task_priority =
         variations::GetVariationParamValue(
             kFieldTrialName, "CapSequencedWorkerPoolsAtUserVisible") == "true"
             ? base::TaskPriority::USER_VISIBLE
             : base::TaskPriority::HIGHEST;
     base::SequencedWorkerPool::EnableWithRedirectionToTaskSchedulerForProcess(
         max_task_priority);
   }
 }
 
 }  // namespace task_scheduler_util