Move a bunch of GC related files to heap/ subdirectory

src/sweeper-thread.h

-// Copyright 2012 the V8 project 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 V8_SWEEPER_THREAD_H_
-#define V8_SWEEPER_THREAD_H_
-
-#include "src/base/atomicops.h"
-#include "src/base/platform/platform.h"
-#include "src/flags.h"
-#include "src/utils.h"
-
-#include "src/spaces.h"
-
-#include "src/heap.h"
-
-namespace v8 {
-namespace internal {
-
-class SweeperThread : public base::Thread {
- public:
-  explicit SweeperThread(Isolate* isolate);
-  ~SweeperThread() {}
-
-  void Run();
-  void Stop();
-  void StartSweeping();
-  void WaitForSweeperThread();
-  bool SweepingCompleted();
-
-  static int NumberOfThreads(int max_available);
-
- private:
-  Isolate* isolate_;
-  Heap* heap_;
-  MarkCompactCollector* collector_;
-  base::Semaphore start_sweeping_semaphore_;
-  base::Semaphore end_sweeping_semaphore_;
-  base::Semaphore stop_semaphore_;
-  volatile base::AtomicWord stop_thread_;
-};
-
-} }  // namespace v8::internal
-
-#endif  // V8_SWEEPER_THREAD_H_