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diff --git a/ipc/glue/IdleSchedulerParent.h b/ipc/glue/IdleSchedulerParent.h
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+++ b/ipc/glue/IdleSchedulerParent.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_IdleSchedulerParent_h__
+#define mozilla_ipc_IdleSchedulerParent_h__
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/LinkedList.h"
+#include "mozilla/ipc/PIdleSchedulerParent.h"
+#include "base/shared_memory.h"
+#include <bitset>
+
+#define NS_IDLE_SCHEDULER_COUNTER_ARRAY_LENGHT 1024
+#define NS_IDLE_SCHEDULER_INDEX_OF_ACTIVITY_COUNTER 0
+#define NS_IDLE_SCHEDULER_INDEX_OF_CPU_COUNTER 1
+
+class nsITimer;
+
+namespace mozilla {
+
+namespace ipc {
+
+class BackgroundParentImpl;
+
+class IdleSchedulerParent final
+    : public PIdleSchedulerParent,
+      public LinkedListElement<IdleSchedulerParent> {
+ public:
+  NS_INLINE_DECL_REFCOUNTING(IdleSchedulerParent)
+
+  IPCResult RecvInitForIdleUse(InitForIdleUseResolver&& aResolve);
+  IPCResult RecvRequestIdleTime(uint64_t aId, TimeDuration aBudget);
+  IPCResult RecvIdleTimeUsed(uint64_t aId);
+  IPCResult RecvSchedule();
+  IPCResult RecvRunningPrioritizedOperation();
+  IPCResult RecvPrioritizedOperationDone();
+  IPCResult RecvRequestGC(RequestGCResolver&& aResolve);
+  IPCResult RecvStartedGC();
+  IPCResult RecvDoneGC();
+
+ private:
+  friend class BackgroundParentImpl;
+  IdleSchedulerParent();
+  ~IdleSchedulerParent();
+
+  static void CalculateNumIdleTasks();
+
+  static int32_t ActiveCount();
+  static void Schedule(IdleSchedulerParent* aRequester);
+  static bool HasSpareCycles(int32_t aActiveCount);
+  static bool HasSpareGCCycles();
+  using PIdleSchedulerParent::SendIdleTime;
+  void SendIdleTime();
+  void SendMayGC();
+
+  static void EnsureStarvationTimer();
+  static void StarvationCallback(nsITimer* aTimer, void* aData);
+
+  uint64_t mCurrentRequestId = 0;
+  // For now we don't really use idle budget for scheduling.  Zero if the
+  // process isn't requestiong or running an idle task.
+  TimeDuration mRequestedIdleBudget;
+
+  // Counting all the prioritized operations the process is doing.
+  uint32_t mRunningPrioritizedOperation = 0;
+
+  // Only one of these may be true at a time, giving three states:
+  // No active GC request, A pending GC request, or a granted GC request.
+  Maybe<RequestGCResolver> mRequestingGC;
+  bool mDoingGC = false;
+
+  uint32_t mChildId = 0;
+
+  // Current state, only one of these may be true at a time.
+  bool IsWaitingForIdle() const { return isInList() && mRequestedIdleBudget; }
+  bool IsDoingIdleTask() const { return !isInList() && mRequestedIdleBudget; }
+  bool IsNotDoingIdleTask() const { return !mRequestedIdleBudget; }
+
+  // Shared memory for counting how many child processes are running
+  // tasks. This memory is shared across all the child processes.
+  // The [0] is used for counting all the processes and
+  // [childId] is for counting per process activity.
+  // This way the global activity can be checked in a fast way by just looking
+  // at [0] value.
+  // [1] is used for cpu count for child processes.
+  static base::SharedMemory* sActiveChildCounter;
+  // A bit is set if there is a child with child Id as the offset.
+  // The bit is used to check per child specific activity counters in
+  // sActiveChildCounter.
+  static std::bitset<NS_IDLE_SCHEDULER_COUNTER_ARRAY_LENGHT>
+      sInUseChildCounters;
+
+  // Processes on this list have requested (but the request hasn't yet been
+  // granted) idle time or to start a GC or both.
+  //
+  // Either or both their mRequestedIdleBudget or mRequestingGC fields are
+  // non-zero.  Child processes not on this list have either been granted all
+  // their requests not made a request ever or since they last finished an idle
+  // or GC task.
+  //
+  // Use the methods above to determine a process' idle time state, or check the
+  // mRequestingGC and mDoingGC fields for the GC state.
+  static LinkedList<IdleSchedulerParent> sIdleAndGCRequests;
+
+  static int32_t sMaxConcurrentIdleTasksInChildProcesses;
+  static uint32_t sMaxConcurrentGCs;
+  static uint32_t sActiveGCs;
+
+  // True if we should record some telemetry for GCs in the next Schedule().
+  // This is set to true by either requesting a GC job or scheduling a GC job.
+  static bool sRecordGCTelemetry;
+  // The current number of waiting GCs.
+  static uint32_t sNumWaitingGC;
+
+  // Counting all the child processes which have at least one prioritized
+  // operation.
+  static uint32_t sChildProcessesRunningPrioritizedOperation;
+
+  // When this hits zero, it's time to free the shared memory and pack up.
+  static uint32_t sChildProcessesAlive;
+
+  static nsITimer* sStarvationPreventer;
+
+  static uint32_t sNumCPUs;
+  static uint32_t sPrefConcurrentGCsMax;
+  static uint32_t sPrefConcurrentGCsCPUDivisor;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_IdleSchedulerParent_h__