Implementing sign-in promo histograms for settings

ios/chrome/browser/prefs/browser_prefs.mm

 // Copyright 2015 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 "ios/chrome/browser/prefs/browser_prefs.h"
 
 #include "components/autofill/core/browser/autofill_manager.h"
 #include "components/browsing_data/core/pref_names.h"
 #include "components/content_settings/core/browser/host_content_settings_map.h"
 #include "components/dom_distiller/core/distilled_page_prefs.h"
@@ skipping 108 matching lines @@
   translate::TranslatePrefs::RegisterProfilePrefs(registry);
   variations::VariationsService::RegisterProfilePrefs(registry);
   ZeroSuggestProvider::RegisterProfilePrefs(registry);
   DesktopPromotionSyncService::RegisterDesktopPromotionUserPrefs(registry);
   RegisterVoiceSearchBrowserStatePrefs(registry);
 
   [BookmarkCollectionView registerBrowserStatePrefs:registry];
   [BookmarkInteractionController registerBrowserStatePrefs:registry];
   [BookmarkPromoController registerBrowserStatePrefs:registry];
   [HandoffManager registerBrowserStatePrefs:registry];
+  registry->RegisterIntegerPref(prefs::kIosSettingsSigninPromoDisplayedCount,
+                                0);
 
   registry->RegisterBooleanPref(prefs::kDataSaverEnabled, false);
   registry->RegisterBooleanPref(
       prefs::kEnableDoNotTrack, false,
       user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
   registry->RegisterBooleanPref(
       prefs::kEnableTranslate, true,
       user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
   registry->RegisterStringPref(prefs::kAcceptLanguages,
                                l10n_util::GetStringUTF8(IDS_ACCEPT_LANGUAGES));
@@ skipping 29 matching lines @@
 }
 
 // This method should be periodically pruned of year+ old migrations.
 void MigrateObsoleteBrowserStatePrefs(PrefService* prefs) {
   // Added 07/2014.
   translate::TranslatePrefs::MigrateUserPrefs(prefs, prefs::kAcceptLanguages);
 
   // Added 08/2015.
   prefs->ClearPref(::prefs::kSigninSharedAuthenticationUserId);
 }