Properly create zero-initialized local memory.

base/metrics/persistent_memory_allocator.h

 // Copyright (c) 2015 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.
 
 #ifndef BASE_METRICS_PERSISTENT_MEMORY_ALLOCATOR_H_
 #define BASE_METRICS_PERSISTENT_MEMORY_ALLOCATOR_H_
 
 #include <stdint.h>
 
 #include <atomic>
@@ skipping 336 matching lines @@
 // save the contents to persistent storage during process shutdown. It is
 // also useful for testing.
 class BASE_EXPORT LocalPersistentMemoryAllocator
     : public PersistentMemoryAllocator {
  public:
   LocalPersistentMemoryAllocator(size_t size, uint64_t id,
                                  base::StringPiece name);
   ~LocalPersistentMemoryAllocator() override;
 
  private:
+  // Allocates a block of local memory of the specified |size|, ensuring that
+  // the memory will not be physically allocated until accessed and will read
+  // as zero when that happens.
+  static void* AllocateLocalMemory(size_t size);
+
+  // Deallocates a block of local |memory| of the specified |size|.
+  static void DeallocateLocalMemory(void* memory, size_t size);
+
   DISALLOW_COPY_AND_ASSIGN(LocalPersistentMemoryAllocator);
 };
 
 
 // This allocator takes a shared-memory object and performs allocation from
 // it. The memory must be previously mapped via Map() or MapAt(). The allocator
 // takes ownership of the memory object.
 class BASE_EXPORT SharedPersistentMemoryAllocator
     : public PersistentMemoryAllocator {
  public:
@@ skipping 41 matching lines @@
 
  private:
   std::unique_ptr<MemoryMappedFile> mapped_file_;
 
   DISALLOW_COPY_AND_ASSIGN(FilePersistentMemoryAllocator);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_PERSISTENT_MEMORY_ALLOCATOR_H_