Use lock-free lazy initialization for static histogram references

chrome/browser/chromeos/boot_times_loader.cc

 // 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/boot_times_loader.h"
 
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/file_path.h"
@@ skipping 241 matching lines @@
     const std::string uma_prefix,
     const std::vector<TimeMarker> login_times) {
   const int kMinTimeMillis = 1;
   const int kMaxTimeMillis = 30000;
   const int kNumBuckets = 100;
   const FilePath log_path(kLogPath);
 
   base::Time first = login_times.front().time();
   base::Time last = login_times.back().time();
   base::TimeDelta total = last - first;
-  scoped_refptr<base::Histogram>total_hist = base::Histogram::FactoryTimeGet(
+  base::Histogram* total_hist = base::Histogram::FactoryTimeGet(
       uma_name,
       base::TimeDelta::FromMilliseconds(kMinTimeMillis),
       base::TimeDelta::FromMilliseconds(kMaxTimeMillis),
       kNumBuckets,
       base::Histogram::kUmaTargetedHistogramFlag);
   total_hist->AddTime(total);
   std::string output =
       base::StringPrintf("%s: %.2f", uma_name.c_str(), total.InSecondsF());
   base::Time prev = first;
   for (unsigned int i = 0; i < login_times.size(); ++i) {
     TimeMarker tm = login_times[i];
     base::TimeDelta since_first = tm.time() - first;
     base::TimeDelta since_prev = tm.time() - prev;
     std::string name;
 
     if (tm.send_to_uma()) {
       name = uma_prefix + tm.name();
-      scoped_refptr<base::Histogram>prev_hist = base::Histogram::FactoryTimeGet(
+      base::Histogram* prev_hist = base::Histogram::FactoryTimeGet(
           name,
           base::TimeDelta::FromMilliseconds(kMinTimeMillis),
           base::TimeDelta::FromMilliseconds(kMaxTimeMillis),
           kNumBuckets,
           base::Histogram::kUmaTargetedHistogramFlag);
       prev_hist->AddTime(since_prev);
     } else {
       name = tm.name();
     }
     output +=
@@ skipping 104 matching lines @@
                               login_time_markers_),
           kLoginTimeWriteDelayMs);
       have_registered_ = false;
     } else {
       AddLoginTimeMarker("LoginRenderNoNetwork", false);
     }
   }
 }
 
 }  // namespace chromeos