Use lock-free lazy initialization for static histogram references

net/base/cookie_monster_unittest.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 <time.h>
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
@@ skipping 2230 matching lines @@
   EXPECT_EQ("http://example.com/",
             CookieMonster::CanonicalCookie::GetCookieSourceFromURL(
                 GURL("http://example.com/test#foo")));
 }
 
 TEST(CookieMonsterTest, HistogramCheck) {
   scoped_refptr<CookieMonster> cm(new CookieMonster(NULL, NULL));
   // Should match call in InitializeHistograms, but doesn't really matter
   // since the histogram should have been initialized by the CM construction
   // above.
-  scoped_refptr<base::Histogram> expired_histogram =
+  base::Histogram* expired_histogram =
       base::Histogram::FactoryGet(
           "Cookie.ExpirationDurationMinutes", 1, 10 * 365 * 24 * 60, 50,
           base::Histogram::kUmaTargetedHistogramFlag);
 
   base::Histogram::SampleSet histogram_set_1;
   expired_histogram->SnapshotSample(&histogram_set_1);
   ASSERT_TRUE(cm->SetCookieWithDetails(
       GURL("http://fake.a.url"), "a", "b", "a.url", "/",
       base::Time::Now() + base::TimeDelta::FromMinutes(59),
       false, false));
 
   base::Histogram::SampleSet histogram_set_2;
   expired_histogram->SnapshotSample(&histogram_set_2);
   EXPECT_EQ(histogram_set_1.TotalCount() + 1,
             histogram_set_2.TotalCount());
 
   // kValidCookieLine creates a session cookie.
   GURL url_google(kUrlGoogle);
   ASSERT_TRUE(cm->SetCookie(url_google, kValidCookieLine));
   expired_histogram->SnapshotSample(&histogram_set_1);
   EXPECT_EQ(histogram_set_2.TotalCount(),
             histogram_set_1.TotalCount());
 }
 
 }  // namespace