Implement cache counting for the simple and memory backends.

net/disk_cache/memory/mem_backend_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_backend_impl.h"
 
 #include "base/logging.h"
 #include "base/sys_info.h"
 #include "net/base/net_errors.h"
 #include "net/disk_cache/cache_util.h"
@@ skipping 166 matching lines @@
 int MemBackendImpl::DoomEntriesSince(const base::Time initial_time,
                                      const CompletionCallback& callback) {
   if (DoomEntriesSince(initial_time))
     return net::OK;
 
   return net::ERR_FAILED;
 }
 
 int MemBackendImpl::CalculateSizeOfAllEntries(
     const CompletionCallback& callback) {
-  // TODO(msramek): Implement.
-  return net::ERR_NOT_IMPLEMENTED;
+  return current_size_;
 }
 
 class MemBackendImpl::MemIterator : public Backend::Iterator {
  public:
   explicit MemIterator(base::WeakPtr<MemBackendImpl> backend)
       : backend_(backend), current_(NULL) {
   }
 
   int OpenNextEntry(Entry** next_entry,
                     const CompletionCallback& callback) override {
@@ skipping 144 matching lines @@
   if (current_size_ > max_size_)
     TrimCache(false);
 }
 
 void MemBackendImpl::SubstractStorageSize(int32 bytes) {
   current_size_ -= bytes;
   DCHECK_GE(current_size_, 0);
 }
 
 }  // namespace disk_cache