Update from https://crrev.com/320343

base/memory/discardable_memory_ashmem.cc

-// 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.
-
-#include "base/memory/discardable_memory_ashmem.h"
-
-#include "base/memory/discardable_memory_ashmem_allocator.h"
-
-namespace base {
-namespace internal {
-
-DiscardableMemoryAshmem::DiscardableMemoryAshmem(
-    size_t bytes,
-    DiscardableMemoryAshmemAllocator* allocator,
-    DiscardableMemoryManager* manager)
-    : bytes_(bytes),
-      allocator_(allocator),
-      manager_(manager),
-      is_locked_(false) {
-  manager_->Register(this, bytes_);
-}
-
-DiscardableMemoryAshmem::~DiscardableMemoryAshmem() {
-  if (is_locked_)
-    Unlock();
-
-  manager_->Unregister(this);
-}
-
-bool DiscardableMemoryAshmem::Initialize() {
-  return Lock() != DISCARDABLE_MEMORY_LOCK_STATUS_FAILED;
-}
-
-DiscardableMemoryLockStatus DiscardableMemoryAshmem::Lock() {
-  DCHECK(!is_locked_);
-
-  bool purged = false;
-  if (!manager_->AcquireLock(this, &purged))
-    return DISCARDABLE_MEMORY_LOCK_STATUS_FAILED;
-
-  is_locked_ = true;
-  return purged ? DISCARDABLE_MEMORY_LOCK_STATUS_PURGED
-                : DISCARDABLE_MEMORY_LOCK_STATUS_SUCCESS;
-}
-
-void DiscardableMemoryAshmem::Unlock() {
-  DCHECK(is_locked_);
-  manager_->ReleaseLock(this);
-  is_locked_ = false;
-}
-
-void* DiscardableMemoryAshmem::Memory() const {
-  DCHECK(is_locked_);
-  DCHECK(ashmem_chunk_);
-  return ashmem_chunk_->Memory();
-}
-
-bool DiscardableMemoryAshmem::AllocateAndAcquireLock() {
-  if (ashmem_chunk_)
-    return ashmem_chunk_->Lock();
-
-  ashmem_chunk_ = allocator_->Allocate(bytes_);
-  return false;
-}
-
-void DiscardableMemoryAshmem::ReleaseLock() {
-  ashmem_chunk_->Unlock();
-}
-
-void DiscardableMemoryAshmem::Purge() {
-  ashmem_chunk_.reset();
-}
-
-}  // namespace internal
-}  // namespace base