[scheduler]: Avoid waking up the scheduler to end long idle periods.

components/scheduler/child/pollable_thread_safe_flag.cc

+// Copyright 2015 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/scheduler/child/pollable_thread_safe_flag.h"
+
+PollableThreadSafeFlag::PollableThreadSafeFlag(base::Lock* write_lock_)
+    : flag_(false), write_lock_(write_lock_) {
+}
+
+PollableThreadSafeFlag::~PollableThreadSafeFlag() {
+}
+
+void PollableThreadSafeFlag::SetWhileLocked(bool value) {
+  write_lock_->AssertAcquired();
+  base::subtle::Release_Store(&flag_, value);
+}
+
+bool PollableThreadSafeFlag::IsSet() const {
+  return base::subtle::Acquire_Load(&flag_) != false;
+}