third_party/blink/public/platform/scheduler/web_thread_scheduler.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 THIRD_PARTY_BLINK_PUBLIC_PLATFORM_SCHEDULER_WEB_THREAD_SCHEDULER_H_
#define THIRD_PARTY_BLINK_PUBLIC_PLATFORM_SCHEDULER_WEB_THREAD_SCHEDULER_H_

#include "base/macros.h"
#include "base/single_thread_task_runner.h"
#include "third_party/blink/public/platform/scheduler/single_thread_idle_task_runner.h"
#include "third_party/blink/public/platform/web_common.h"

namespace blink {
namespace scheduler {

class BLINK_PLATFORM_EXPORT WebThreadScheduler {
 public:
  virtual ~WebThreadScheduler() = default;

  // Returns the default task runner.
  virtual scoped_refptr<base::SingleThreadTaskRunner> DefaultTaskRunner() = 0;

  // Returns the idle task runner. Tasks posted to this runner may be reordered
  // relative to other task types and may be starved for an arbitrarily long
  // time if no idle time is available.
  virtual scoped_refptr<SingleThreadIdleTaskRunner> IdleTaskRunner() = 0;

  virtual scoped_refptr<base::SingleThreadTaskRunner> IPCTaskRunner() = 0;

  // Returns true if there is high priority work pending on the main thread
  // and the caller should yield to let the scheduler service that work. Note
  // that this is a stricter condition than |IsHighPriorityWorkAnticipated|,
  // restricted to the case where real work is pending.
  // Must be called from the thread this scheduler was created on.
  virtual bool ShouldYieldForHighPriorityWork() = 0;

  // Returns true if a currently running idle task could exceed its deadline
  // without impacting user experience too much. This should only be used if
  // there is a task which cannot be pre-empted and is likely to take longer
  // than the largest expected idle task deadline. It should NOT be polled to
  // check whether more work can be performed on the current idle task after
  // its deadline has expired - post a new idle task for the continuation of the
  // work in this case.
  // Must be called from the thread this scheduler was created on.
  virtual bool CanExceedIdleDeadlineIfRequired() const = 0;

  // Shuts down the scheduler by dropping any remaining pending work in the work
  // queues. After this call any work posted to the task runners will be
  // silently dropped.
  virtual void Shutdown() = 0;

 protected:
  WebThreadScheduler() = default;
  DISALLOW_COPY_AND_ASSIGN(WebThreadScheduler);
};

}  // namespace scheduler
}  // namespace blink

#endif  // THIRD_PARTY_BLINK_PUBLIC_PLATFORM_SCHEDULER_WEB_THREAD_SCHEDULER_H_