Add Browser Task Scheduler Flags

chrome/browser/chrome_browser_main.cc

 // Copyright (c) 2012 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 "chrome/browser/chrome_browser_main.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 19 matching lines @@
 #include "base/path_service.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/run_loop.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/string_split.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/sys_info.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/platform_thread.h"
 #include "base/time/default_tick_clock.h"
 #include "base/time/time.h"
 #include "base/trace_event/trace_event.h"
 #include "base/values.h"
 #include "build/build_config.h"
 #include "cc/base/switches.h"
 #include "chrome/browser/about_flags.h"
@@ skipping 337 matching lines @@
                          : FOREGROUND_FILE_IO_WORKER_POOL;
   }
   return is_background ? BACKGROUND_WORKER_POOL : FOREGROUND_WORKER_POOL;
 }
 
 // Initializes the Default Browser Task Scheduler if there is a valid variation
 // parameter for the field trial.
 void MaybeInitializeTaskScheduler() {
   static constexpr char kFieldTrialName[] = "BrowserScheduler";
   std::map<std::string, std::string> variation_params;
-  if (!variations::GetVariationParams(kFieldTrialName, &variation_params))
+  if (!variations::GetVariationParams(kFieldTrialName, &variation_params)) {
+    DCHECK(!base::CommandLine::ForCurrentProcess()->HasSwitch(
+        switches::kEnableBrowserTaskScheduler))
+        << "The Browser Task Scheduler remains disabled with "
+        << switches::kEnableBrowserTaskScheduler
+        << " because there is no available variation param for this build or "
+           " the task scheduler is disabled in chrome://flags.";
     return;
+  }
 
   using ThreadPriority = base::ThreadPriority;
   using IORestriction = base::SchedulerWorkerPoolParams::IORestriction;
   struct SchedulerWorkerPoolPredefinedParams {
     const char* name;
     ThreadPriority priority_hint;
     IORestriction io_restriction;
   };
   static const SchedulerWorkerPoolPredefinedParams kAllPredefinedParams[] = {
     {"Background", ThreadPriority::BACKGROUND, IORestriction::DISALLOWED},
@@ skipping 1791 matching lines @@
   chromeos::CrosSettings::Shutdown();
 #endif  // defined(OS_CHROMEOS)
 #endif  // defined(OS_ANDROID)
 }
 
 // Public members:
 
 void ChromeBrowserMainParts::AddParts(ChromeBrowserMainExtraParts* parts) {
   chrome_extra_parts_.push_back(parts);
 }