Revert of Add ScopedTaskEnvironment::ExecutionControlMode.

base/test/scoped_task_environment.cc

Index: base/test/scoped_task_environment.cc
diff --git a/base/test/scoped_task_environment.cc b/base/test/scoped_task_environment.cc
index 7ca8af0735abaa4e9713debd2f8bdabc47438620..672ffb053b542c5fc4b6b747a17f40076270acc2 100644
--- a/base/test/scoped_task_environment.cc
+++ b/base/test/scoped_task_environment.cc
@@ -5,12 +5,8 @@
 #include "base/test/scoped_task_environment.h"
 
 #include "base/run_loop.h"
-#include "base/synchronization/condition_variable.h"
-#include "base/synchronization/lock.h"
-#include "base/task_scheduler/post_task.h"
+#include "base/task_scheduler/scheduler_worker_pool_params.h"
 #include "base/task_scheduler/task_scheduler.h"
-#include "base/task_scheduler/task_scheduler_impl.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 
 namespace base {
@@ -25,70 +21,25 @@
   // MessageLoop::TaskObserver:
   void WillProcessTask(const PendingTask& pending_task) override {}
   void DidProcessTask(const PendingTask& pending_task) override {
-    ++task_count_;
+    ran_task_ = true;
   }
 
-  int task_count() const { return task_count_; }
+  bool ran_task() const { return ran_task_; }
 
  private:
-  int task_count_ = 0;
-
+  bool ran_task_ = false;
   DISALLOW_COPY_AND_ASSIGN(TaskObserver);
 };
 
 }  // namespace
 
-class ScopedTaskEnvironment::TestTaskTracker
-    : public internal::TaskSchedulerImpl::TaskTrackerType {
- public:
-  TestTaskTracker(ScopedTaskEnvironment* outer);
-
-  void SetTaskQueueEmptyClosure(OnceClosure task_queue_empty_closure);
-
-  // Allow running tasks.
-  void AllowRunRask();
-
-  // Disallow running tasks. No-ops and returns false if a task is running.
-  bool DisallowRunTasks();
-
- private:
-  friend class ScopedTaskEnvironment;
-
-  // internal::TaskSchedulerImpl::TaskTrackerType:
-  void PerformRunTask(std::unique_ptr<internal::Task> task,
-                      const SequenceToken& sequence_token) override;
-
-  ScopedTaskEnvironment* const outer_;
-
-  // Synchronizes accesses to members below.
-  Lock lock_;
-
-  // Closure posted to the main thread when the task queue becomes empty.
-  OnceClosure task_queue_empty_closure_;
-
-  // True if running tasks is allowed.
-  bool can_run_tasks_ = true;
-
-  // Signaled when |can_run_tasks_| becomes true.
-  ConditionVariable can_run_tasks_cv_;
-
-  // Number of tasks that are currently running.
-  int num_tasks_running_ = 0;
-
-  DISALLOW_COPY_AND_ASSIGN(TestTaskTracker);
-};
-
-ScopedTaskEnvironment::ScopedTaskEnvironment(
-    MainThreadType main_thread_type,
-    ExecutionControlMode execution_control_mode)
-    : execution_control_mode_(execution_control_mode),
-      message_loop_(main_thread_type == MainThreadType::DEFAULT
+ScopedTaskEnvironment::ScopedTaskEnvironment(MainThreadType main_thread_type)
+    : message_loop_(main_thread_type == MainThreadType::DEFAULT
                         ? MessageLoop::TYPE_DEFAULT
                         : (main_thread_type == MainThreadType::UI
                                ? MessageLoop::TYPE_UI
-                               : MessageLoop::TYPE_IO)),
-      task_tracker_(new TestTaskTracker(this)) {
-  CHECK(!TaskScheduler::GetInstance());
+                               : MessageLoop::TYPE_IO)) {
+  DCHECK(!TaskScheduler::GetInstance());
 
   // Instantiate a TaskScheduler with 1 thread in each of its 4 pools. Threads
   // stay alive even when they don't have work.
@@ -97,14 +48,10 @@
   const SchedulerWorkerPoolParams worker_pool_params(
       SchedulerWorkerPoolParams::StandbyThreadPolicy::ONE, kMaxThreads,
       kSuggestedReclaimTime);
-  TaskScheduler::SetInstance(MakeUnique<internal::TaskSchedulerImpl>(
-      "ScopedTaskEnvironment", WrapUnique(task_tracker_)));
+  TaskScheduler::Create("ScopedTaskEnvironment");
   task_scheduler_ = TaskScheduler::GetInstance();
   TaskScheduler::GetInstance()->Start({worker_pool_params, worker_pool_params,
                                        worker_pool_params, worker_pool_params});
-
-  if (execution_control_mode_ == ExecutionControlMode::QUEUED)
-    CHECK(task_tracker_->DisallowRunTasks());
 }
 
 ScopedTaskEnvironment::~ScopedTaskEnvironment() {
@@ -112,10 +59,10 @@
   // infinite post loop in the remaining work but this isn't possible right now
   // because base::~MessageLoop() didn't use to do this and adding it here would
   // make the migration away from MessageLoop that much harder.
-  CHECK_EQ(TaskScheduler::GetInstance(), task_scheduler_);
+
+  DCHECK_EQ(TaskScheduler::GetInstance(), task_scheduler_);
   // Without FlushForTesting(), DeleteSoon() and ReleaseSoon() tasks could be
   // skipped, resulting in memory leaks.
-  task_tracker_->AllowRunRask();
   TaskScheduler::GetInstance()->FlushForTesting();
   TaskScheduler::GetInstance()->Shutdown();
   TaskScheduler::GetInstance()->JoinForTesting();
@@ -129,104 +76,15 @@
 
 void ScopedTaskEnvironment::RunUntilIdle() {
   for (;;) {
-    RunLoop run_loop;
+    TaskScheduler::GetInstance()->FlushForTesting();
 
-    // Register a closure to stop running tasks on the main thread when the
-    // TaskScheduler queue becomes empty.
-    task_tracker_->SetTaskQueueEmptyClosure(run_loop.QuitWhenIdleClosure());
-
-    // The closure registered above may never run if the TaskScheduler queue
-    // starts empty. Post a TaskScheduler tasks to make sure that the queue
-    // doesn't start empty.
-    PostTask(FROM_HERE, BindOnce(&DoNothing));
-
-    // Run main thread and TaskScheduler tasks.
-    task_tracker_->AllowRunRask();
     TaskObserver task_observer;
     MessageLoop::current()->AddTaskObserver(&task_observer);
-    run_loop.Run();
+    RunLoop().RunUntilIdle();
     MessageLoop::current()->RemoveTaskObserver(&task_observer);
 
-    // If the ExecutionControlMode is QUEUED and DisallowRunTasks() fails,
-    // another iteration is required to make sure that RunUntilIdle() doesn't
-    // return while TaskScheduler tasks are still allowed to run.
-    //
-    // If tasks other than the QuitWhenIdle closure ran on the main thread, they
-    // may have posted TaskScheduler tasks that didn't run yet. Another
-    // iteration is required to run them.
-    //
-    // Note: DisallowRunTasks() fails when a TaskScheduler task is running. A
-    // TaskScheduler task may be running after the TaskScheduler queue became
-    // empty even if no tasks ran on the main thread in these cases:
-    // - An undelayed task became ripe for execution.
-    // - A task was posted from an external thread.
-    if ((execution_control_mode_ == ExecutionControlMode::QUEUED &&
-         task_tracker_->DisallowRunTasks()) ||
-        task_observer.task_count() == 1) {
+    if (!task_observer.ran_task())
       return;
-    }
-  }
-}
-
-ScopedTaskEnvironment::TestTaskTracker::TestTaskTracker(
-    ScopedTaskEnvironment* outer)
-    : outer_(outer), can_run_tasks_cv_(&lock_) {}
-
-void ScopedTaskEnvironment::TestTaskTracker::SetTaskQueueEmptyClosure(
-    OnceClosure task_queue_empty_closure) {
-  AutoLock auto_lock(lock_);
-  CHECK(!task_queue_empty_closure_);
-  task_queue_empty_closure_ = std::move(task_queue_empty_closure);
-}
-
-void ScopedTaskEnvironment::TestTaskTracker::AllowRunRask() {
-  AutoLock auto_lock(lock_);
-  can_run_tasks_ = true;
-  can_run_tasks_cv_.Broadcast();
-}
-
-bool ScopedTaskEnvironment::TestTaskTracker::DisallowRunTasks() {
-  AutoLock auto_lock(lock_);
-
-  // Can't disallow run task if there are tasks running.
-  if (num_tasks_running_ > 0)
-    return false;
-
-  can_run_tasks_ = false;
-  return true;
-}
-
-void ScopedTaskEnvironment::TestTaskTracker::PerformRunTask(
-    std::unique_ptr<internal::Task> task,
-    const SequenceToken& sequence_token) {
-  {
-    AutoLock auto_lock(lock_);
-
-    while (!can_run_tasks_)
-      can_run_tasks_cv_.Wait();
-
-    ++num_tasks_running_;
-  }
-
-  internal::TaskSchedulerImpl::TaskTrackerType::PerformRunTask(std::move(task),
-                                                               sequence_token);
-
-  {
-    AutoLock auto_lock(lock_);
-
-    CHECK_GT(num_tasks_running_, 0);
-    CHECK(can_run_tasks_);
-
-    --num_tasks_running_;
-
-    // Notify the main thread when no undelayed tasks are queued and no task
-    // other than the current one is running.
-    if (num_tasks_running_ == 0 &&
-        GetNumPendingUndelayedTasksForTesting() == 1 &&
-        task_queue_empty_closure_) {
-      outer_->GetMainThreadTaskRunner()->PostTask(
-          FROM_HERE, std::move(task_queue_empty_closure_));
-    }
   }
 }