[M56] Revert "Enable Initialization of the Task Scheduler by Default in the Browser Process"

components/task_scheduler_util/initialization_util.cc

Index: components/task_scheduler_util/initialization_util.cc
diff --git a/components/task_scheduler_util/initialization_util.cc b/components/task_scheduler_util/initialization_util.cc
index 8893d47dd86188c4426978a192a62992bc618c18..748eae3a21bf00797099dd42209914564fb59f0c 100644
--- a/components/task_scheduler_util/initialization_util.cc
+++ b/components/task_scheduler_util/initialization_util.cc
@@ -4,8 +4,6 @@
 
 #include "components/task_scheduler_util/initialization_util.h"
 
-#include <map>
-#include <string>
 #include <vector>
 
 #include "base/bind.h"
@@ -15,13 +13,9 @@
 #include "base/strings/string_split.h"
 #include "base/task_scheduler/initialization_util.h"
 #include "base/task_scheduler/scheduler_worker_pool_params.h"
-#include "base/task_scheduler/switches.h"
 #include "base/task_scheduler/task_scheduler.h"
 #include "base/task_scheduler/task_traits.h"
-#include "base/threading/sequenced_worker_pool.h"
 #include "base/time/time.h"
-#include "build/build_config.h"
-#include "components/variations/variations_associated_data.h"
 
 namespace task_scheduler_util {
 
@@ -101,27 +95,9 @@ size_t WorkerPoolIndexForTraits(const base::TaskTraits& traits) {
   return is_background ? BACKGROUND_WORKER_POOL : FOREGROUND_WORKER_POOL;
 }
 
-std::map<std::string, std::string> GetDefaultBrowserVariationParams() {
-  std::map<std::string, std::string> variation_params;
-#if defined(OS_ANDROID) || defined(OS_IOS)
-  variation_params["Background"] = "2;8;0.1;0;30000";
-  variation_params["BackgroundFileIO"] = "2;8;0.1;0;30000";
-  variation_params["Foreground"] = "3;8;0.3;0;30000";
-  variation_params["ForegroundFileIO"] = "3;8;0.3;0;30000";
-#else
-  variation_params["Background"] = "3;8;0.1;0;30000";
-  variation_params["BackgroundFileIO"] = "3;8;0.1;0;30000";
-  variation_params["Foreground"] = "8;32;0.3;0;30000";
-  variation_params["ForegroundFileIO"] = "8;32;0.3;0;30000";
-#endif  // defined(OS_ANDROID) || defined(OS_IOS)
-  return variation_params;
-}
+}  // namespace
 
-// Converts a browser-based |variation_params| to
-// std::vector<base::SchedulerWorkerPoolParams>. Returns an empty vector on
-// failure.
-std::vector<base::SchedulerWorkerPoolParams>
-VariationsParamsToBrowserSchedulerWorkerPoolParams(
+bool InitializeDefaultTaskScheduler(
     const std::map<std::string, std::string>& variation_params) {
   using ThreadPriority = base::ThreadPriority;
   using IORestriction = base::SchedulerWorkerPoolParams::IORestriction;
@@ -138,13 +114,14 @@ VariationsParamsToBrowserSchedulerWorkerPoolParams(
   };
   static_assert(arraysize(kAllPredefinedParams) == WORKER_POOL_COUNT,
                 "Mismatched Worker Pool Types and Predefined Parameters");
+
   std::vector<base::SchedulerWorkerPoolParams> params_vector;
   for (const auto& predefined_params : kAllPredefinedParams) {
     const auto pair = variation_params.find(predefined_params.name);
     if (pair == variation_params.end()) {
       DLOG(ERROR) << "Missing Worker Pool Configuration: "
                   << predefined_params.name;
-      return std::vector<base::SchedulerWorkerPoolParams>();
+      return false;
     }
 
     const WorkerPoolVariationValues variation_values =
@@ -154,7 +131,7 @@ VariationsParamsToBrowserSchedulerWorkerPoolParams(
         variation_values.detach_period.is_zero()) {
       DLOG(ERROR) << "Invalid Worker Pool Configuration: " <<
           predefined_params.name << " [" << pair->second << "]";
-      return std::vector<base::SchedulerWorkerPoolParams>();
+      return false;
     }
 
     params_vector.emplace_back(predefined_params.name,
@@ -164,38 +141,13 @@ VariationsParamsToBrowserSchedulerWorkerPoolParams(
                                variation_values.threads,
                                variation_values.detach_period);
   }
-  DCHECK_EQ(WORKER_POOL_COUNT, params_vector.size());
-  return params_vector;
-}
 
-}  // namespace
+  DCHECK_EQ(WORKER_POOL_COUNT, params_vector.size());
 
-void InitializeDefaultBrowserTaskScheduler() {
-  static constexpr char kFieldTrialName[] = "BrowserScheduler";
-  std::map<std::string, std::string> variation_params;
-  if (!variations::GetVariationParams(kFieldTrialName, &variation_params))
-    variation_params = GetDefaultBrowserVariationParams();
-
-  auto params_vector =
-      VariationsParamsToBrowserSchedulerWorkerPoolParams(variation_params);
-  if (params_vector.empty()) {
-    variation_params = GetDefaultBrowserVariationParams();
-    params_vector =
-        VariationsParamsToBrowserSchedulerWorkerPoolParams(variation_params);
-    DCHECK(!params_vector.empty());
-  }
   base::TaskScheduler::CreateAndSetDefaultTaskScheduler(
       params_vector, base::Bind(WorkerPoolIndexForTraits));
 
-  // TODO(gab): Remove this when http://crbug.com/622400 concludes.
-  const auto sequenced_worker_pool_param =
-      variation_params.find("RedirectSequencedWorkerPools");
-  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kDisableBrowserTaskScheduler) &&
-      sequenced_worker_pool_param != variation_params.end() &&
-      sequenced_worker_pool_param->second == "true") {
-    base::SequencedWorkerPool::RedirectToTaskSchedulerForProcess();
-  }
+  return true;
 }
 
 }  // namespace task_scheduler_util