[Mac] A couple of improvements for DiscardableMemory

base/memory/discardable_memory_malloc.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_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;
+  return Lock() != DISCARDABLE_MEMORY_LOCK_STATUS_FAILED;
 }
 
 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