Use lock-free lazy initialization for static histogram references

net/base/cookie_monster.h

 // 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.
 
 // Brought to you by the letter D and the number 2.
 
 #ifndef NET_BASE_COOKIE_MONSTER_H_
 #define NET_BASE_COOKIE_MONSTER_H_
 #pragma once
 
@@ skipping 451 matching lines @@
   // Initialize the above variables; should only be called from
   // the constructor.
   void InitializeHistograms();
 
   // The resolution of our time isn't enough, so we do something
   // ugly and increment when we've seen the same time twice.
   base::Time CurrentTime();
 
   // Histogram variables; see CookieMonster::InitializeHistograms() in
   // cookie_monster.cc for details.
-  scoped_refptr<base::Histogram> histogram_expiration_duration_minutes_;
-  scoped_refptr<base::Histogram> histogram_between_access_interval_minutes_;
-  scoped_refptr<base::Histogram> histogram_evicted_last_access_minutes_;
-  scoped_refptr<base::Histogram> histogram_count_;
-  scoped_refptr<base::Histogram> histogram_domain_count_;
-  scoped_refptr<base::Histogram> histogram_etldp1_count_;
-  scoped_refptr<base::Histogram> histogram_domain_per_etldp1_count_;
-  scoped_refptr<base::Histogram> histogram_number_duplicate_db_cookies_;
-  scoped_refptr<base::Histogram> histogram_cookie_deletion_cause_;
-  scoped_refptr<base::Histogram> histogram_time_get_;
-  scoped_refptr<base::Histogram> histogram_time_load_;
+  base::Histogram* histogram_expiration_duration_minutes_;
+  base::Histogram* histogram_between_access_interval_minutes_;
+  base::Histogram* histogram_evicted_last_access_minutes_;
+  base::Histogram* histogram_count_;
+  base::Histogram* histogram_domain_count_;
+  base::Histogram* histogram_etldp1_count_;
+  base::Histogram* histogram_domain_per_etldp1_count_;
+  base::Histogram* histogram_number_duplicate_db_cookies_;
+  base::Histogram* histogram_cookie_deletion_cause_;
+  base::Histogram* histogram_time_get_;
+  base::Histogram* histogram_time_load_;
 
   CookieMap cookies_;
 
   // Indicates whether the cookie store has been initialized. This happens
   // lazily in InitStoreIfNecessary().
   bool initialized_;
 
   // Indicates whether this cookie monster uses the new effective domain
   // key scheme or not.
   ExpiryAndKeyScheme expiry_and_key_scheme_;
@@ skipping 299 matching lines @@
  private:
   DISALLOW_COPY_AND_ASSIGN(PersistentCookieStore);
 };
 
 class CookieList : public std::vector<CookieMonster::CanonicalCookie> {
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_COOKIE_MONSTER_H_