Revert of scheduler: Add a base directory

components/scheduler/child/task_queue.h

+// Copyright 2015 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 COMPONENTS_SCHEDULER_CHILD_TASK_QUEUE_H_
+#define COMPONENTS_SCHEDULER_CHILD_TASK_QUEUE_H_
+
+#include "base/message_loop/message_loop.h"
+#include "base/single_thread_task_runner.h"
+#include "components/scheduler/scheduler_export.h"
+
+namespace scheduler {
+
+class SCHEDULER_EXPORT TaskQueue : public base::SingleThreadTaskRunner {
+ public:
+  TaskQueue() {}
+
+  // Unregisters the task queue after which no tasks posted to it will run and
+  // the TaskQueueManager's reference to it will be released soon.
+  virtual void UnregisterTaskQueue() = 0;
+
+  // Post a delayed task at an absolute desired run time instead of a time
+  // delta from the current time.
+  virtual bool PostDelayedTaskAt(const tracked_objects::Location& from_here,
+                                 const base::Closure& task,
+                                 base::TimeTicks desired_run_time) = 0;
+
+  enum QueuePriority {
+    // Queues with control priority will run before any other queue, and will
+    // explicitly starve other queues. Typically this should only be used for
+    // private queues which perform control operations.
+    CONTROL_PRIORITY,
+    // Queues with high priority will be selected preferentially over normal or
+    // best effort queues. The selector will ensure that high priority queues
+    // cannot completely starve normal priority queues.
+    HIGH_PRIORITY,
+    // Queues with normal priority are the default.
+    NORMAL_PRIORITY,
+    // Queues with best effort priority will only be run if all other queues are
+    // empty. They can be starved by the other queues.
+    BEST_EFFORT_PRIORITY,
+    // Queues with this priority are never run.  Must be penultimate entry.
+    DISABLED_PRIORITY,
+    // Must be the last entry.
+    QUEUE_PRIORITY_COUNT,
+    FIRST_QUEUE_PRIORITY = CONTROL_PRIORITY,
+  };
+
+  // Keep TaskQueue::PumpPolicyToString in sync with this enum.
+  enum class PumpPolicy {
+    // Tasks posted to an incoming queue with an AUTO pump policy will be
+    // automatically scheduled for execution or transferred to the work queue
+    // automatically.
+    AUTO,
+    // Tasks posted to an incoming queue with an AFTER_WAKEUP pump policy
+    // will be scheduled for execution or transferred to the work queue
+    // automatically but only after another queue has executed a task.
+    AFTER_WAKEUP,
+    // Tasks posted to an incoming queue with a MANUAL will not be
+    // automatically scheduled for execution or transferred to the work queue.
+    // Instead, the selector should call PumpQueue() when necessary to bring
+    // in new tasks for execution.
+    MANUAL,
+    // Must be last entry.
+    PUMP_POLICY_COUNT,
+    FIRST_PUMP_POLICY = AUTO,
+  };
+
+  // Keep TaskQueue::WakeupPolicyToString in sync with this enum.
+  enum class WakeupPolicy {
+    // Tasks run on a queue with CAN_WAKE_OTHER_QUEUES wakeup policy can
+    // cause queues with the AFTER_WAKEUP PumpPolicy to be woken up.
+    CAN_WAKE_OTHER_QUEUES,
+    // Tasks run on a queue with DONT_WAKE_OTHER_QUEUES won't cause queues
+    // with the AFTER_WAKEUP PumpPolicy to be woken up.
+    DONT_WAKE_OTHER_QUEUES,
+    // Must be last entry.
+    WAKEUP_POLICY_COUNT,
+    FIRST_WAKEUP_POLICY = CAN_WAKE_OTHER_QUEUES,
+  };
+
+  enum class QueueState {
+    // A queue in the EMPTY state is empty and has no tasks in either the
+    // work or incoming task queue.
+    EMPTY,
+    // A queue in the NEEDS_PUMPING state has no tasks in the work task queue,
+    // but has tasks in the incoming task queue which can be pumped to make them
+    // runnable.
+    NEEDS_PUMPING,
+    // A queue in the HAS_WORK state has tasks in the work task queue which
+    // are runnable.
+    HAS_WORK,
+  };
+
+  // Options for constructing a TaskQueue. Once set the |name|,
+  // |should_monitor_quiescence| and |wakeup_policy| are immutable. The
+  // |pump_policy| can be mutated with |SetPumpPolicy()|.
+  struct Spec {
+    // Note |name| must have application lifetime.
+    explicit Spec(const char* name)
+        : name(name),
+          should_monitor_quiescence(false),
+          pump_policy(TaskQueue::PumpPolicy::AUTO),
+          wakeup_policy(TaskQueue::WakeupPolicy::CAN_WAKE_OTHER_QUEUES),
+          should_notify_observers(true) {}
+
+    Spec SetShouldMonitorQuiescence(bool should_monitor) {
+      should_monitor_quiescence = should_monitor;
+      return *this;
+    }
+
+    Spec SetPumpPolicy(PumpPolicy policy) {
+      pump_policy = policy;
+      return *this;
+    }
+
+    Spec SetWakeupPolicy(WakeupPolicy policy) {
+      wakeup_policy = policy;
+      return *this;
+    }
+
+    Spec SetShouldNotifyObservers(bool run_observers) {
+      should_notify_observers = run_observers;
+      return *this;
+    }
+
+    const char* name;
+    bool should_monitor_quiescence;
+    TaskQueue::PumpPolicy pump_policy;
+    TaskQueue::WakeupPolicy wakeup_policy;
+    bool should_notify_observers;
+  };
+
+  // Returns true if the queue priority is not
+  // TaskQueueSelector::DISABLED_PRIORITY. NOTE this must be called on the
+  // thread this TaskQueue was created by.
+  virtual bool IsQueueEnabled() const = 0;
+
+  // Returns true if there no tasks in either the work or incoming task queue.
+  // Note that this function involves taking a lock, so calling it has some
+  // overhead. NOTE this must be called on the thread this TaskQueue was created
+  // by.
+  virtual bool IsQueueEmpty() const;
+
+  // Returns the QueueState. Note that this function involves taking a lock, so
+  // calling it has some overhead.
+  virtual QueueState GetQueueState() const = 0;
+
+  // Can be called on any thread.
+  virtual const char* GetName() const = 0;
+
+  // Set the priority of the queue to |priority|. NOTE this must be called on
+  // the thread this TaskQueue was created by.
+  virtual void SetQueuePriority(QueuePriority priority) = 0;
+
+  // Set the pumping policy of the queue to |pump_policy|. NOTE this must be
+  // called on the thread this TaskQueue was created by.
+  virtual void SetPumpPolicy(PumpPolicy pump_policy) = 0;
+
+  // Reloads new tasks from the incoming queue into the work queue, regardless
+  // of whether the work queue is empty or not. After this, the function ensures
+  // that the tasks in the work queue, if any, are scheduled for execution.
+  //
+  // This function only needs to be called if automatic pumping is disabled.
+  // By default automatic pumping is enabled for all queues. NOTE this must be
+  // called on the thread this TaskQueue was created by.
+  virtual void PumpQueue() = 0;
+
+  // These functions can only be called on the same thread that the task queue
+  // manager executes its tasks on.
+  virtual void AddTaskObserver(
+      base::MessageLoop::TaskObserver* task_observer) = 0;
+  virtual void RemoveTaskObserver(
+      base::MessageLoop::TaskObserver* task_observer) = 0;
+
+ protected:
+  ~TaskQueue() override {}
+
+  DISALLOW_COPY_AND_ASSIGN(TaskQueue);
+};
+
+}  // namespace scheduler
+
+#endif  // COMPONENTS_SCHEDULER_CHILD_TASK_QUEUE_H_