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