scheduler: Move the Blink scheduler into Blink

components/scheduler/base/pollable_thread_safe_flag.h

-// 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.
-
-#ifndef COMPONENTS_SCHEDULER_BASE_POLLABLE_THREAD_SAFE_FLAG_H_
-#define COMPONENTS_SCHEDULER_BASE_POLLABLE_THREAD_SAFE_FLAG_H_
-
-#include "base/atomicops.h"
-#include "base/macros.h"
-#include "base/synchronization/lock.h"
-
-// A PollableThreadSafeFlag can be polled without requiring a lock, but can only
-// be updated if a lock is held. This enables lock-free checking as to whether a
-// condition has changed, while protecting operations which update the condition
-// with a lock. You must ensure that the flag is only updated within the same
-// lock-protected critical section as any other variables on which the condition
-// depends.
-class PollableThreadSafeFlag {
- public:
-  explicit PollableThreadSafeFlag(base::Lock* write_lock);
-  ~PollableThreadSafeFlag();
-
-  // Set the flag. May only be called if |write_lock| is held.
-  void SetWhileLocked(bool value);
-
-  // Returns true iff the flag is set to true.
-  bool IsSet() const;
-
- private:
-  base::subtle::Atomic32 flag_;
-  base::Lock* write_lock_;  // Not owned.
-
-  DISALLOW_COPY_AND_ASSIGN(PollableThreadSafeFlag);
-};
-
-#endif  // COMPONENTS_SCHEDULER_BASE_POLLABLE_THREAD_SAFE_FLAG_H_