Moved zones and zone related stuff in its own directory.

src/base/accounting-allocator.h

-// Copyright 2016 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_BASE_ACCOUNTING_ALLOCATOR_H_
-#define V8_BASE_ACCOUNTING_ALLOCATOR_H_
-
-#include "src/base/atomicops.h"
-#include "src/base/macros.h"
-
-namespace v8 {
-namespace base {
-
-class AccountingAllocator {
- public:
-  AccountingAllocator() = default;
-  virtual ~AccountingAllocator() = default;
-
-  // Returns nullptr on failed allocation.
-  virtual void* Allocate(size_t bytes);
-  virtual void Free(void* memory, size_t bytes);
-
-  size_t GetCurrentMemoryUsage() const;
-  size_t GetMaxMemoryUsage() const;
-
- private:
-  AtomicWord current_memory_usage_ = 0;
-  AtomicWord max_memory_usage_ = 0;
-
-  DISALLOW_COPY_AND_ASSIGN(AccountingAllocator);
-};
-
-}  // namespace base
-}  // namespace v8
-
-#endif  // V8_BASE_ACCOUNTING_ALLOCATOR_H_