base: Remove DiscardableMemory::CreateLockedMemory.

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/memory/discardable_memory_allocator.h"
-
 namespace base {
 
-// static
-scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemory(
-    size_t size) {
-  return DiscardableMemoryAllocator::GetInstance()
-      ->AllocateLockedDiscardableMemory(size);
+DiscardableMemory::DiscardableMemory() {
+}
+
+DiscardableMemory::~DiscardableMemory() {
 }
 
 }  // namespace base