base: Add uncached malloc based discardable memory type.

base/memory/discardable_memory_malloc.cc

+// Copyright 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_malloc.h"
+
+#include "base/logging.h"
+
+namespace base {
+namespace internal {
+
+DiscardableMemoryMalloc::DiscardableMemoryMalloc(size_t size) : size_(size) {
+}
+
+DiscardableMemoryMalloc::~DiscardableMemoryMalloc() {
+}
+
+bool DiscardableMemoryMalloc::Initialize() {
+  return Lock() == DISCARDABLE_MEMORY_LOCK_STATUS_PURGED;
+}
+
+DiscardableMemoryLockStatus DiscardableMemoryMalloc::Lock() {
+  DCHECK(!memory_);
+
+  memory_.reset(static_cast<uint8*>(malloc(size_)));
+  if (!memory_)
+    return DISCARDABLE_MEMORY_LOCK_STATUS_FAILED;
+
+  return DISCARDABLE_MEMORY_LOCK_STATUS_PURGED;
+}
+
+void DiscardableMemoryMalloc::Unlock() {
+  DCHECK(memory_);
+  memory_.reset();
+}
+
+void* DiscardableMemoryMalloc::Memory() const {
+  DCHECK(memory_);
+  return memory_.get();
+}
+
+}  // namespace internal
+}  // namespace base