scheduler: Move the Blink scheduler into Blink

components/scheduler/base/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/base/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;
-}