Use factory to create histograms, and refcounts to track lifetimes...

net/disk_cache/stats_histogram.cc

 // Copyright (c) 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_histogram.h"
 
 #include "base/logging.h"
 #include "net/disk_cache/stats.h"
 
 namespace disk_cache {
 
 // Static.
 const Stats* StatsHistogram::stats_ = NULL;
 
+scoped_refptr<StatsHistogram> StatsHistogram::StatsHistogramFactoryGet(
+    const std::string& name) {
+  scoped_refptr<Histogram> histogram(NULL);
+
+  Sample minimum = 1;
+  Sample maximum = disk_cache::Stats::kDataSizesLength - 1;
+  size_t bucket_count = disk_cache::Stats::kDataSizesLength;
+
+  if (StatisticsRecorder::FindHistogram(name, &histogram)) {
+    DCHECK(histogram.get() != NULL);
+  } else {
+    histogram = new StatsHistogram(name, minimum, maximum, bucket_count);
+    scoped_refptr<Histogram> registered_histogram(NULL);
+    StatisticsRecorder::FindHistogram(name, &registered_histogram);
+    if (registered_histogram.get() != NULL &&
+        registered_histogram.get() != histogram.get())
+      histogram = registered_histogram;
+  }
+
+  DCHECK(HISTOGRAM == histogram->histogram_type());
+  DCHECK(histogram->HasConstructorArguments(minimum, maximum, bucket_count));
+
+  // We're preparing for an otherwise unsafe upcast by ensuring we have the
+  // proper class type.
+  Histogram* temp_histogram = histogram.get();
+  StatsHistogram* temp_stats_histogram =
+      static_cast<StatsHistogram*>(temp_histogram);
+  scoped_refptr<StatsHistogram> return_histogram = temp_stats_histogram;
+  return return_histogram;
+}
+
 bool StatsHistogram::Init(const Stats* stats) {
   DCHECK(stats);
   if (stats_)
     return false;
 
   SetFlags(kUmaTargetedHistogramFlag);
 
   // We support statistics report for only one cache.
   init_ = true;
   stats_ = stats;
@@ skipping 21 matching lines @@
   stats_->Snapshot(&my_sample);
 
   *sample = my_sample;
 
   // Only report UMA data once.
   StatsHistogram* mutable_me = const_cast<StatsHistogram*>(this);
   mutable_me->ClearFlags(kUmaTargetedHistogramFlag);
 }
 
 }  // namespace disk_cache