Update from https://crrev.com/320931

base/memory/discardable_memory_mac.cc

-// Copyright (c) 2013 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.h"
-
-#include "base/logging.h"
-#include "base/memory/discardable_memory_shmem.h"
-#include "base/memory/scoped_ptr.h"
-
-namespace base {
-
-// static
-void DiscardableMemory::GetSupportedTypes(
-    std::vector<DiscardableMemoryType>* types) {
-  const DiscardableMemoryType supported_types[] = {
-    DISCARDABLE_MEMORY_TYPE_SHMEM
-  };
-  types->assign(supported_types, supported_types + arraysize(supported_types));
-}
-
-// static
-scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemoryWithType(
-    DiscardableMemoryType type, size_t size) {
-  switch (type) {
-    case DISCARDABLE_MEMORY_TYPE_SHMEM:
-      return make_scoped_ptr(new internal::DiscardableMemoryShmem(size));
-    case DISCARDABLE_MEMORY_TYPE_NONE:
-      NOTREACHED();
-      return nullptr;
-  }
-
-  NOTREACHED();
-  return nullptr;
-}
-
-}  // namespace base