Use lock-free lazy initialization for static histogram references

chrome/browser/autocomplete/history_quick_provider.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/autocomplete/history_quick_provider.h"
 
 #include "base/basictypes.h"
 #include "base/i18n/break_iterator.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
@@ skipping 53 matching lines @@
   // TODO(pkasting): We should just block here until this loads.  Any time
   // someone unloads the history backend, we'll get inconsistent inline
   // autocomplete behavior here.
   if (GetIndex()) {
     base::TimeTicks start_time = base::TimeTicks::Now();
     DoAutocomplete();
     if (input.text().size() < 6) {
       base::TimeTicks end_time = base::TimeTicks::Now();
       std::string name = "HistoryQuickProvider.QueryIndexTime." +
           base::IntToString(input.text().size());
-      scoped_refptr<base::Histogram> counter = base::Histogram::FactoryGet(
+      base::Histogram* counter = base::Histogram::FactoryGet(
           name, 1, 1000, 50, base::Histogram::kUmaTargetedHistogramFlag);
       counter->Add(static_cast<int>((end_time - start_time).InMilliseconds()));
     }
     UpdateStarredStateOfMatches();
   }
 }
 
 // HistoryQuickProvider matches are currently not deletable.
 // TODO(mrossetti): Determine when a match should be deletable.
 void HistoryQuickProvider::DeleteMatch(const AutocompleteMatch& match) {}
@@ skipping 125 matching lines @@
       ++i;
     } while ((i < match_count) && (offset == matches[i].offset));
     if (offset < text_length) {
       spans.push_back(ACMatchClassification(offset,
                                             ACMatchClassification::NONE));
     }
   }
 
   return spans;
 }