Keep track of byte usage of the memory cache backend

net/disk_cache/memory/mem_entry_impl.cc

 // 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.
 
 #include "net/disk_cache/memory/mem_entry_impl.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 235 matching lines @@
 
 bool MemEntryImpl::CouldBeSparse() const {
   DCHECK_EQ(PARENT_ENTRY, type());
   return (children_.get() != nullptr);
 }
 
 int MemEntryImpl::ReadyForSparseIO(const CompletionCallback& callback) {
   return net::OK;
 }
 
+size_t MemEntryImpl::EstimateMemoryUsage() const {
+  // Subtlety: the entries in children_ are not double counted, as the entry
+  // pointers won't be followed by EstimateMemoryUsage.
+  return base::trace_event::EstimateMemoryUsage(data_) +
+         base::trace_event::EstimateMemoryUsage(key_) +
+         base::trace_event::EstimateMemoryUsage(children_);
+}
+
 // ------------------------------------------------------------------------
 
 MemEntryImpl::MemEntryImpl(MemBackendImpl* backend,
                            const ::std::string& key,
                            int child_id,
                            MemEntryImpl* parent,
                            net::NetLog* net_log)
     : key_(key),
       ref_count_(0),
       child_id_(child_id),
@@ skipping 313 matching lines @@
          scanned_len += first_pos - current_child_offset;
          break;
       }
     }
     scanned_len += kMaxSparseEntrySize - current_child_offset;
   }
   return scanned_len;
 }
 
 }  // namespace disk_cache