Keep track of byte usage of the memory cache backend

net/disk_cache/memory/mem_entry_impl.h

 // Copyright (c) 2012 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 NET_DISK_CACHE_MEMORY_MEM_ENTRY_IMPL_H_
 #define NET_DISK_CACHE_MEMORY_MEM_ENTRY_IMPL_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <unordered_map>
 #include <vector>
 
 #include "base/containers/linked_list.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/time/time.h"
+#include "base/trace_event/memory_usage_estimator.h"
 #include "net/base/net_export.h"
 #include "net/disk_cache/disk_cache.h"
 #include "net/log/net_log_with_source.h"
 
 namespace net {
 class NetLog;
 }
 
 namespace disk_cache {
 
@@ skipping 94 matching lines @@
                       IOBuffer* buf,
                       int buf_len,
                       const CompletionCallback& callback) override;
   int GetAvailableRange(int64_t offset,
                         int len,
                         int64_t* start,
                         const CompletionCallback& callback) override;
   bool CouldBeSparse() const override;
   void CancelSparseIO() override {}
   int ReadyForSparseIO(const CompletionCallback& callback) override;
+  size_t EstimateMemoryUsage() const;
 
  private:
   MemEntryImpl(MemBackendImpl* backend,
                const std::string& key,
                int child_id,
                MemEntryImpl* parent,
                net::NetLog* net_log);
 
   using EntryMap = std::unordered_map<int, MemEntryImpl*>;
 
@@ skipping 42 matching lines @@
   bool doomed_;               // True if this entry was removed from the cache.
 
   net::NetLogWithSource net_log_;
 
   DISALLOW_COPY_AND_ASSIGN(MemEntryImpl);
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_MEMORY_MEM_ENTRY_IMPL_H_