Use lock-free lazy initialization for static histogram references

chrome/browser/chromeos/external_metrics.cc

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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 "chrome/browser/chromeos/external_metrics.h"
 
 #include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
@@ skipping 67 matching lines @@
   int sample, min, max, nbuckets;
   char name[128];   // length must be consistent with sscanf format below.
   int n = sscanf(histogram_data, "%127s %d %d %d %d",
                  name, &sample, &min, &max, &nbuckets);
   if (n != 5) {
     LOG(ERROR) << "bad histogram request: " << histogram_data;
     return;
   }
   // Do not use the UMA_HISTOGRAM_... macros here.  They cache the Histogram
   // instance and thus only work if |name| is constant.
-  scoped_refptr<base::Histogram> counter = base::Histogram::FactoryGet(
+  base::Histogram* counter = base::Histogram::FactoryGet(
       name, min, max, nbuckets, base::Histogram::kUmaTargetedHistogramFlag);
   counter->Add(sample);
 }
 
 void ExternalMetrics::RecordLinearHistogram(const char* histogram_data) {
   int sample, max;
   char name[128];   // length must be consistent with sscanf format below.
   int n = sscanf(histogram_data, "%127s %d %d", name, &sample, &max);
   if (n != 3) {
     LOG(ERROR) << "bad linear histogram request: " << histogram_data;
     return;
   }
   // Do not use the UMA_HISTOGRAM_... macros here.  They cache the Histogram
   // instance and thus only work if |name| is constant.
-  scoped_refptr<base::Histogram> counter = base::LinearHistogram::FactoryGet(
+  base::Histogram* counter = base::LinearHistogram::FactoryGet(
       name, 1, max, max + 1, base::Histogram::kUmaTargetedHistogramFlag);
   counter->Add(sample);
 }
 
 void ExternalMetrics::CollectEvents() {
   const char* event_file_path = "/var/log/metrics/uma-events";
   struct stat stat_buf;
   int result;
   if (!test_path_.empty()) {
     event_file_path = test_path_.value().c_str();
@@ skipping 112 matching lines @@
 void ExternalMetrics::ScheduleCollector() {
   bool result;
   result = BrowserThread::PostDelayedTask(
     BrowserThread::FILE, FROM_HERE, NewRunnableMethod(
         this, &chromeos::ExternalMetrics::CollectEventsAndReschedule),
     kExternalMetricsCollectionIntervalMs);
   DCHECK(result);
 }
 
 }  // namespace chromeos