components/scheduler/child/child_scheduler.h

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef COMPONENTS_SCHEDULER_CHILD_CHILD_SCHEDULER_H_
   6 #define COMPONENTS_SCHEDULER_CHILD_CHILD_SCHEDULER_H_
   7
   8 #include "base/message_loop/message_loop.h"
   9 #include "components/scheduler/child/single_thread_idle_task_runner.h"
  10 #include "components/scheduler/child/task_queue.h"
  11 #include "components/scheduler/scheduler_export.h"
  12
  13 namespace base {
  14 class MessageLoop;
  15 }
  16
  17 namespace scheduler {
  18
  19 class SCHEDULER_EXPORT ChildScheduler {
  20  public:
  21   virtual ~ChildScheduler() {}
  22
  23   // Returns the default task runner.
  24   // TODO(alexclarke): Change this to return a SingleThreadIdleTaskRunner.
  25   virtual scoped_refptr<TaskQueue> DefaultTaskRunner() = 0;
  26
  27   // Returns the idle task runner. Tasks posted to this runner may be reordered
  28   // relative to other task types and may be starved for an arbitrarily long
  29   // time if no idle time is available.
  30   virtual scoped_refptr<SingleThreadIdleTaskRunner> IdleTaskRunner() = 0;
  31
  32   // Returns true if there is high priority work pending on the main thread
  33   // and the caller should yield to let the scheduler service that work. Note
  34   // that this is a stricter condition than |IsHighPriorityWorkAnticipated|,
  35   // restricted to the case where real work is pending.
  36   // Must be called from the thread this scheduler was created on.
  37   virtual bool ShouldYieldForHighPriorityWork() = 0;
  38
  39   // Returns true if a currently running idle task could exceed its deadline
  40   // without impacting user experience too much. This should only be used if
  41   // there is a task which cannot be pre-empted and is likely to take longer
  42   // than the largest expected idle task deadline. It should NOT be polled to
  43   // check whether more work can be performed on the current idle task after
  44   // its deadline has expired - post a new idle task for the continuation of the
  45   // work in this case.
  46   // Must be called from the thread this scheduler was created on.
  47   virtual bool CanExceedIdleDeadlineIfRequired() const = 0;
  48
  49   // Adds or removes a task observer from the scheduler. The observer will be
  50   // notified before and after every executed task. These functions can only be
  51   // called on the thread this scheduler was created on.
  52   virtual void AddTaskObserver(
  53       base::MessageLoop::TaskObserver* task_observer) = 0;
  54   virtual void RemoveTaskObserver(
  55       base::MessageLoop::TaskObserver* task_observer) = 0;
  56
  57   // Shuts down the scheduler by dropping any remaining pending work in the work
  58   // queues. After this call any work posted to the task runners will be
  59   // silently dropped.
  60   virtual void Shutdown() = 0;
  61
  62  protected:
  63   ChildScheduler() {}
  64   DISALLOW_COPY_AND_ASSIGN(ChildScheduler);
  65 };
  66
  67 }  // namespace scheduler
  68
  69 #endif  // COMPONENTS_SCHEDULER_CHILD_CHILD_SCHEDULER_H_