Update from https://crrev.com/320931

base/memory/discardable_memory.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.h"
 
-#include "base/lazy_instance.h"
-#include "base/logging.h"
+#include "base/memory/discardable_memory_shmem.h"
 
 namespace base {
-namespace {
-
-const struct TypeNamePair {
-  DiscardableMemoryType type;
-  const char* name;
-} kTypeNamePairs[] = {
-  { DISCARDABLE_MEMORY_TYPE_SHMEM, "shmem" }
-};
-
-DiscardableMemoryType g_preferred_type = DISCARDABLE_MEMORY_TYPE_NONE;
-
-struct DefaultPreferredType {
-  DefaultPreferredType() : value(DISCARDABLE_MEMORY_TYPE_NONE) {
-    std::vector<DiscardableMemoryType> supported_types;
-    DiscardableMemory::GetSupportedTypes(&supported_types);
-    DCHECK(!supported_types.empty());
-    value = supported_types[0];
-  }
-  DiscardableMemoryType value;
-};
-LazyInstance<DefaultPreferredType>::Leaky g_default_preferred_type =
-    LAZY_INSTANCE_INITIALIZER;
-
-}  // namespace
-
-// static
-DiscardableMemoryType DiscardableMemory::GetNamedType(
-    const std::string& name) {
-  for (size_t i = 0; i < arraysize(kTypeNamePairs); ++i) {
-    if (name == kTypeNamePairs[i].name)
-      return kTypeNamePairs[i].type;
-  }
-
-  return DISCARDABLE_MEMORY_TYPE_NONE;
-}
-
-// static
-const char* DiscardableMemory::GetTypeName(DiscardableMemoryType type) {
-  for (size_t i = 0; i < arraysize(kTypeNamePairs); ++i) {
-    if (type == kTypeNamePairs[i].type)
-      return kTypeNamePairs[i].name;
-  }
-
-  return "unknown";
-}
-
-// static
-void DiscardableMemory::SetPreferredType(DiscardableMemoryType type) {
-  // NONE is a reserved value and not a valid default type.
-  DCHECK_NE(DISCARDABLE_MEMORY_TYPE_NONE, type);
-
-  // Make sure this function is only called once before the first call
-  // to GetPreferredType().
-  DCHECK_EQ(DISCARDABLE_MEMORY_TYPE_NONE, g_preferred_type);
-
-  g_preferred_type = type;
-}
-
-// static
-DiscardableMemoryType DiscardableMemory::GetPreferredType() {
-  if (g_preferred_type == DISCARDABLE_MEMORY_TYPE_NONE)
-    g_preferred_type = g_default_preferred_type.Get().value;
-
-  return g_preferred_type;
-}
 
 // static
 scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemory(
     size_t size) {
-  return CreateLockedMemoryWithType(GetPreferredType(), size);
+  return make_scoped_ptr(new internal::DiscardableMemoryShmem(size));
 }
 
 }  // namespace base