Update from https://crrev.com/320343

base/memory/discardable_memory_mach.h

-// Copyright 2014 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 BASE_MEMORY_DISCARDABLE_MEMORY_MACH_H_
-#define BASE_MEMORY_DISCARDABLE_MEMORY_MACH_H_
-
-#include "base/memory/discardable_memory.h"
-
-#include "base/mac/scoped_mach_vm.h"
-#include "base/memory/discardable_memory_manager.h"
-
-namespace base {
-namespace internal {
-
-class DiscardableMemoryMach
-    : public DiscardableMemory,
-      public internal::DiscardableMemoryManagerAllocation {
- public:
-  explicit DiscardableMemoryMach(size_t bytes);
-  ~DiscardableMemoryMach() override;
-
-  bool Initialize();
-
-  // Overridden from DiscardableMemory:
-  DiscardableMemoryLockStatus Lock() override;
-  void Unlock() override;
-  void* Memory() const override;
-
-  // Overridden from internal::DiscardableMemoryManagerAllocation:
-  bool AllocateAndAcquireLock() override;
-  void ReleaseLock() override;
-  void Purge() override;
-
- private:
-  mac::ScopedMachVM memory_;
-  const size_t bytes_;
-  bool is_locked_;
-
-  DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryMach);
-};
-
-}  // namespace internal
-}  // namespace base
-
-#endif  // BASE_MEMORY_DISCARDABLE_MEMORY_MACH_H_