TaskScheduler: Make the worker pools of TaskSchedulerImpl configurable

base/task_scheduler/task_scheduler_impl.h

 // 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.
 
 #ifndef BASE_TASK_SCHEDULER_TASK_SCHEDULER_IMPL_H_
 #define BASE_TASK_SCHEDULER_TASK_SCHEDULER_IMPL_H_
 
+#include <map>
 #include <memory>
+#include <string>
 
 #include "base/base_export.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/task_runner.h"
 #include "base/task_scheduler/delayed_task_manager.h"
 #include "base/task_scheduler/sequence.h"
 #include "base/task_scheduler/task_scheduler.h"
 #include "base/task_scheduler/task_tracker.h"
 #include "base/task_scheduler/task_traits.h"
 
 namespace base {
 namespace internal {
 
 class SchedulerServiceThread;
 class SchedulerThreadPoolImpl;
 
 // Default TaskScheduler implementation. This class is thread-safe.
 class BASE_EXPORT TaskSchedulerImpl : public TaskScheduler {
  public:
-  // Creates and returns an initialized TaskSchedulerImpl. CHECKs on failure to
-  // do so (never returns null).
-  static std::unique_ptr<TaskSchedulerImpl> Create();
+  // Creates and returns an initialized TaskSchedulerImpl. CHECKs on failure
+  // (never returns null). |variation_params| is used to configure the scheduler
+  // (can be empty).
+  static std::unique_ptr<TaskSchedulerImpl> Create(
+      const std::map<std::string, std::string>& variation_params);
 
   // Destroying a TaskSchedulerImpl is not allowed in production; it is always
   // leaked. In tests, it can only be destroyed after JoinForTesting() has
   // returned.
   ~TaskSchedulerImpl() override;
 
   // TaskScheduler:
   void PostTaskWithTraits(const tracked_objects::Location& from_here,
                           const TaskTraits& traits,
                           const Closure& task) override;
   scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits(
       const TaskTraits& traits,
       ExecutionMode execution_mode) override;
   void Shutdown() override;
 
   // Joins all threads of this scheduler. Tasks that are already running are
   // allowed to complete their execution. This can only be called once.
   void JoinForTesting();
 
  private:
   TaskSchedulerImpl();
 
-  void Initialize();
+  void Initialize(const std::map<std::string, std::string>& variation_params);
 
   // Returns the thread pool that runs Tasks with |traits|.
   SchedulerThreadPool* GetThreadPoolForTraits(const TaskTraits& traits);
 
   // Callback invoked when a non-single-thread |sequence| isn't empty after a
   // worker thread pops a Task from it.
   void ReEnqueueSequenceCallback(scoped_refptr<Sequence> sequence);
 
   // Callback invoked when the delayed run time is changed from the
   // DelayedTaskManager.
@@ skipping 21 matching lines @@
   WaitableEvent join_for_testing_returned_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(TaskSchedulerImpl);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_TASK_SCHEDULER_IMPL_H_