Disk Cache: Second pass (and final) to allow multiple instances...

net/disk_cache/stats.cc

 // Copyright (c) 2006-2008 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/stats.h"
 
 #include "base/logging.h"
 #include "base/string_util.h"
 #include "net/disk_cache/backend_impl.h"
 
@@ skipping 105 matching lines @@
     if (!LoadStats(backend, address, &stats))
       return false;
   } else {
     if (!CreateStats(backend, &address, &stats))
       return false;
     *storage_addr = address.value();
   }
 
   storage_addr_ = address.value();
   backend_ = backend;
-  if (!size_histogram_.get()) {
-    // Stats may be reused when the cache is re-created, but we want only one
-    // histogram at any given time.
-    size_histogram_.reset(new StatsHistogram("DiskCache.SizeStats"));
-    size_histogram_->Init(this);
-  }
 
   memcpy(data_sizes_, stats.data_sizes, sizeof(data_sizes_));
   memcpy(counters_, stats.counters, sizeof(counters_));
 
+  // It seems impossible to support this histogram for more than one
+  // simultaneous objects with the current infrastructure.
+  static bool first_time = true;
+  if (first_time) {
+    first_time = false;
+    // ShouldReportAgain() will re-enter this object.
+    if (!size_histogram_.get() && backend->cache_type() == net::DISK_CACHE &&
+        backend->ShouldReportAgain()) {
+      // Stats may be reused when the cache is re-created, but we want only one
+      // histogram at any given time.
+      size_histogram_.reset(new StatsHistogram("DiskCache.SizeStats"));
+      size_histogram_->Init(this);
+    }
+  }
+
   return true;
 }
 
 Stats::~Stats() {
   Store();
 }
 
 // The array will be filled this way:
 //  index      size
 //    0       [0, 1024)
@@ skipping 155 matching lines @@
   stats.signature = kDiskSignature;
   stats.size = sizeof(stats);
   memcpy(stats.data_sizes, data_sizes_, sizeof(data_sizes_));
   memcpy(stats.counters, counters_, sizeof(counters_));
 
   Addr address(storage_addr_);
   StoreStats(backend_, address, &stats);
 }
 
 }  // namespace disk_cache