Refactor histogram_persistence to be a class.

chrome/browser/chrome_browser_field_trials.cc

 // Copyright (c) 2012 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/chrome_browser_field_trials.h"
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/feature_list.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_base.h"
-#include "base/metrics/histogram_persistence.h"
+#include "base/metrics/persistent_histogram_allocator.h"
 #include "base/strings/string_util.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "chrome/common/chrome_switches.h"
 #include "components/metrics/metrics_pref_names.h"
 
 #if defined(OS_ANDROID)
 #include "chrome/browser/chrome_browser_field_trials_mobile.h"
 #else
 #include "chrome/browser/chrome_browser_field_trials_desktop.h"
 #endif
 
 namespace {
 
 // Check for feature enabling the use of persistent histogram storage and
 // create an appropriate allocator for such if so.
 void InstantiatePersistentHistograms() {
   if (base::FeatureList::IsEnabled(base::kPersistentHistogramsFeature)) {
     const char kAllocatorName[] = "BrowserMetrics";
     // Create persistent/shared memory and allow histograms to be stored in it.
     // Memory that is not actualy used won't be physically mapped by the system.
     // BrowserMetrics usage peaked around 95% of 2MiB as of 2016-02-20.
-    base::SetPersistentHistogramMemoryAllocator(
-        new base::LocalPersistentMemoryAllocator(3 << 20,     // 3 MiB
-                                                 0x935DDD43,  // SHA1(B...M...)
-                                                 kAllocatorName));
-    base::GetPersistentHistogramMemoryAllocator()->CreateTrackingHistograms(
+    base::PersistentHistogramAllocator::CreateGlobalAllocatorOnLocalMemory(
+        3 << 20,     // 3 MiB
+        0x935DDD43,  // SHA1(BrowserMetrics)
         kAllocatorName);
+    base::PersistentHistogramAllocator::GetGlobalAllocator()
+        ->CreateTrackingHistograms(kAllocatorName);
   }
 }
 
 }  // namespace
 
 ChromeBrowserFieldTrials::ChromeBrowserFieldTrials(
     const base::CommandLine& parsed_command_line)
     : parsed_command_line_(parsed_command_line) {
 }
 
 ChromeBrowserFieldTrials::~ChromeBrowserFieldTrials() {
 }
 
 void ChromeBrowserFieldTrials::SetupFieldTrials() {
   // Field trials that are shared by all platforms.
   InstantiateDynamicTrials();
 
 #if defined(OS_ANDROID)
   chrome::SetupMobileFieldTrials(parsed_command_line_);
 #else
   chrome::SetupDesktopFieldTrials(parsed_command_line_);
 #endif
 }
 
 void ChromeBrowserFieldTrials::InstantiateDynamicTrials() {
   // Persistent histograms must be enabled as soon as possible.
   InstantiatePersistentHistograms();
 }