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 {
+  return base::trace_event::EstimateMemoryUsage(data_) +
+         base::trace_event::EstimateMemoryUsage(key_) +
+         base::trace_event::EstimateMemoryUsage(children_);

[xunjieli, 2017/02/27 18:51:31]

I suppose the |children_| entries are accounted for in the backend's
|iru_list_|?

[jkarlin, 2017/02/28 13:10:50]

Ah, you're right. Switched to using GetStorageSize().

[xunjieli, 2017/02/28 14:51:23]

Ah, sorry for the confusion, the previous patchset is correct. Could you change
it back?
|children_| is a std::unique_ptr<std::unordered_map<int, MemEntryImpl*>>.
base::trace_event::EstimateMemoryUsage(children_) will count the size of the
MemEntryImpl pointer as stored in the map but not the underlying type. 

If the underlying MemEntryImpl are accounted for in the backend, then we are
good here. EMU(children_) gives exactly what we want (the allocation is just for
the map and there is no double counting of the underlying MemEntryImpl).

[jkarlin, 2017/02/28 15:50:54]

Done.

+}
+
 // ------------------------------------------------------------------------
 
 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