[Not for review] Discardable memory emulation

webkit/glue/web_discardable_memory_impl.cc

 // Copyright (c) 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 "webkit/glue/web_discardable_memory_impl.h"
 
 namespace webkit_glue {
 
-WebDiscardableMemoryImpl::WebDiscardableMemoryImpl()
-    : discardable_(new base::DiscardableMemory()) {
+WebDiscardableMemoryImpl::WebDiscardableMemoryImpl() {
+  if (base::DiscardableMemoryProvider* provider =
+      base::DiscardableMemoryProvider::GetInstance())
+    discardable_.reset(provider->CreateDiscardableMemory());
 }
 
 WebDiscardableMemoryImpl::~WebDiscardableMemoryImpl() {}
 
 bool WebDiscardableMemoryImpl::InitializeAndLock(size_t size) {
+  if (!discardable_)
+    return false;
   return discardable_->InitializeAndLock(size);
 }
 
 bool WebDiscardableMemoryImpl::lock() {
+  if (!discardable_)
+    return false;
+
   base::LockDiscardableMemoryStatus status = discardable_->Lock();
   switch (status) {
     case base::DISCARDABLE_MEMORY_SUCCESS:
       return true;
     case base::DISCARDABLE_MEMORY_PURGED:
       discardable_->Unlock();
       return false;
     default:
       discardable_.reset();
       return false;
   }
 }
 
 void* WebDiscardableMemoryImpl::data() {
+  if (!discardable_)
+    return NULL;
   return discardable_->Memory();
 }
 
 void WebDiscardableMemoryImpl::unlock() {
+  if (!discardable_)
+    return;
   discardable_->Unlock();
 }
 
 }  // namespace webkit_glue