Extract AD policy scheduler into separate class

components/policy/core/common/policy_scheduler.cc

Index: components/policy/core/common/policy_scheduler.cc
diff --git a/components/policy/core/common/policy_scheduler.cc b/components/policy/core/common/policy_scheduler.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b4c4bd1a1309b21406f9e202d3d145a35ac122ee
--- /dev/null
+++ b/components/policy/core/common/policy_scheduler.cc
@@ -0,0 +1,74 @@
+// Copyright 2017 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.
+
+#include "components/policy/core/common/policy_scheduler.h"
+
+#include "base/memory/ptr_util.h"
+#include "base/threading/thread_task_runner_handle.h"
+
+namespace policy {
+
+PolicyScheduler::PolicyScheduler(Task task,
+                                 SchedulerCallback callback,
+                                 base::TimeDelta interval)
+    : task_(task), callback_(callback), interval_(interval) {
+  ScheduleTaskNow();
+}
+
+PolicyScheduler::~PolicyScheduler() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+}
+
+void PolicyScheduler::ScheduleTaskNow() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  ScheduleDelayedTask(base::TimeDelta());
+}
+
+void PolicyScheduler::ScheduleDelayedTask(base::TimeDelta delay) {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
+  if (job_) {
+    job_->Cancel();
+  }
+  job_ = base::MakeUnique<base::CancelableClosure>(base::Bind(
+      &PolicyScheduler::RunScheduledTask, weak_ptr_factory_.GetWeakPtr()));
+  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(FROM_HERE,
+                                                       job_->callback(), delay);
+}
+
+void PolicyScheduler::ScheduleNextTask() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
+  base::TimeDelta interval = overlap_ ? base::TimeDelta() : interval_;
+  const base::TimeTicks now(base::TimeTicks::Now());
+  // Time uses saturated arithmetics thus no under/overflow possible.
+  const base::TimeDelta delay = last_task_ + interval - now;
+  // Clamping delay to non-negative values just to be on the safe side.
+  ScheduleDelayedTask(std::max(base::TimeDelta(), delay));
+}
+
+void PolicyScheduler::RunScheduledTask() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
+  if (task_in_progress_) {
+    overlap_ = true;
+    return;
+  }
+
+  overlap_ = false;
+  task_in_progress_ = true;
+  task_.Run(base::BindOnce(&PolicyScheduler::OnTaskDone,
+                           weak_ptr_factory_.GetWeakPtr()));
+}
+
+void PolicyScheduler::OnTaskDone(bool success) {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
+  task_in_progress_ = false;
+  last_task_ = base::TimeTicks::Now();
+  callback_.Run(success);
+  ScheduleNextTask();
+}
+
+}  // namespace policy