Add an idle task to periodically sweep canceled delayed tasks

third_party/WebKit/Source/platform/scheduler/child/idle_canceled_delayed_task_sweeper.cc

Index: third_party/WebKit/Source/platform/scheduler/child/idle_canceled_delayed_task_sweeper.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/child/idle_canceled_delayed_task_sweeper.cc b/third_party/WebKit/Source/platform/scheduler/child/idle_canceled_delayed_task_sweeper.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ed969fb9ebec69feaa5b50f291afda01b5c66008
--- /dev/null
+++ b/third_party/WebKit/Source/platform/scheduler/child/idle_canceled_delayed_task_sweeper.cc
@@ -0,0 +1,42 @@
+// 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 "platform/scheduler/child/idle_canceled_delayed_task_sweeper.h"
+
+#include "base/bind.h"
+
+namespace blink {
+namespace scheduler {
+
+namespace {
+const int kDelayedTaskSweepIntervalSeconds = 30;
+}
+
+IdleCanceledDelayedTaskSweeper::IdleCanceledDelayedTaskSweeper(
+    const char* tracing_category,
+    SchedulerHelper* scheduler_helper,
+    scoped_refptr<SingleThreadIdleTaskRunner> idle_task_runner)
+    : tracing_category_(tracing_category),
+      scheduler_helper_(scheduler_helper),
+      idle_task_runner_(idle_task_runner),
+      weak_factory_(this) {
+  PostIdleTask();
+}
+
+void IdleCanceledDelayedTaskSweeper::PostIdleTask() {
+  idle_task_runner_->PostDelayedIdleTask(
+      FROM_HERE, base::TimeDelta::FromSeconds(kDelayedTaskSweepIntervalSeconds),
+      base::Bind(&IdleCanceledDelayedTaskSweeper::SweepIdleTask,
+                 weak_factory_.GetWeakPtr()));
+}
+
+void IdleCanceledDelayedTaskSweeper::SweepIdleTask(base::TimeTicks deadline) {
+  TRACE_EVENT0(tracing_category_,
+               "IdleCanceledDelayedTaskSweeper::SweepIdleTask");
+  scheduler_helper_->SweepCanceledDelayedTasks();
+  PostIdleTask();
+}
+
+}  // namespace scheduler
+}  // namespace blink