Reduce memory usage in DelayedPersistentAllocation.

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 832 matching lines @@
 
  private:
   // The underlying object that does the actual allocation of memory. Its
   // lifetime must exceed that of all DelayedPersistentAllocation objects
   // that use it.
   PersistentMemoryAllocator* const allocator_;
 
   // The desired type and size of the allocated segment plus the offset
   // within it for the defined request.
   const uint32_t type_;
-  const size_t size_;
-  const size_t offset_;
+  const uint32_t size_;
+  const uint32_t offset_;
 
   // Flag indicating if allocation should be made iterable when done.
   const bool make_iterable_;
 
   // The location at which a reference to the allocated segment is to be
   // stored once the allocation is complete. If multiple delayed allocations
   // share the same pointer then an allocation on one will amount to an
   // allocation for all.
   volatile std::atomic<Reference>* const reference_;
 
   // No DISALLOW_COPY_AND_ASSIGN as it's okay to copy/move these objects.
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_PERSISTENT_MEMORY_ALLOCATOR_H_