Add UMA for the content suggestions settings

chrome/browser/android/ntp/content_suggestions_notifier_service.cc

 // Copyright 2016 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/android/ntp/content_suggestions_notifier_service.h"
 
 #include <algorithm>
 
 #include "base/android/application_status_listener.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
 #include "chrome/browser/android/ntp/content_suggestions_notification_helper.h"
 #include "chrome/browser/notifications/notification.h"
 #include "chrome/browser/notifications/notification_handler.h"
 #include "chrome/browser/ntp_snippets/ntp_snippets_features.h"
 #include "chrome/browser/ntp_snippets/ntp_snippets_metrics.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/pref_names.h"
 #include "components/ntp_snippets/content_suggestions_service.h"
 #include "components/pref_registry/pref_registry_syncable.h"
 #include "components/prefs/pref_service.h"
@@ skipping 207 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(NotifyingObserver);
 };
 
 ContentSuggestionsNotifierService::ContentSuggestionsNotifierService(
     Profile* profile,
     ContentSuggestionsService* suggestions)
     : profile_(profile), suggestions_service_(suggestions) {
   ContentSuggestionsNotificationHelper::FlushCachedMetrics();
   UpdateObserverRegistrationState();
+
+  UMA_HISTOGRAM_BOOLEAN("ContentSuggestions.Preferences.Notifications",
+                        IsEnabled());
 }
 
 ContentSuggestionsNotifierService::~ContentSuggestionsNotifierService() =
     default;
 
 void ContentSuggestionsNotifierService::RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
   registry->RegisterBooleanPref(prefs::kContentSuggestionsNotificationsEnabled,
                                 true);
   registry->RegisterIntegerPref(
@@ skipping 20 matching lines @@
 
 void ContentSuggestionsNotifierService::UpdateObserverRegistrationState() {
   if (observer_ && !IsEnabled()) {
     suggestions_service_->RemoveObserver(observer_.get());
     observer_.reset();
   } else if (IsEnabled() && !observer_) {
     observer_.reset(new NotifyingObserver(suggestions_service_, profile_));
     suggestions_service_->AddObserver(observer_.get());
   }
 }