Update from https://crrev.com/316786

base/memory/discardable_memory_mach.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_mach.h"
 
 #include <mach/mach.h>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
@@ skipping 45 matching lines @@
     : memory_(0, 0), bytes_(mach_vm_round_page(bytes)), is_locked_(false) {
   g_manager.Pointer()->Register(this, bytes);
 }
 
 DiscardableMemoryMach::~DiscardableMemoryMach() {
   if (is_locked_)
     Unlock();
   g_manager.Pointer()->Unregister(this);
 }
 
-// static
-void DiscardableMemoryMach::PurgeForTesting() {
-  int state = 0;
-  vm_purgable_control(mach_task_self(), 0, VM_PURGABLE_PURGE_ALL, &state);
-}
-
 bool DiscardableMemoryMach::Initialize() {
   return Lock() != DISCARDABLE_MEMORY_LOCK_STATUS_FAILED;
 }
 
 DiscardableMemoryLockStatus DiscardableMemoryMach::Lock() {
   DCHECK(!is_locked_);
 
   bool purged = false;
   if (!g_manager.Pointer()->AcquireLock(this, &purged))
     return DISCARDABLE_MEMORY_LOCK_STATUS_FAILED;
@@ skipping 65 matching lines @@
   ret = vm_protect(
       mach_task_self(), memory_.address(), memory_.size(), FALSE, VM_PROT_NONE);
   MACH_DCHECK(ret == KERN_SUCCESS, ret) << "vm_protect";
 #endif
 }
 
 void DiscardableMemoryMach::Purge() {
   memory_.reset();
 }
 
-bool DiscardableMemoryMach::IsMemoryResident() const {
-  return true;
-}
-
 }  // namespace internal
 }  // namespace base