Add UMA for the content suggestions settings

chrome/browser/android/ntp/content_suggestions_notifier_service.cc

Index: chrome/browser/android/ntp/content_suggestions_notifier_service.cc
diff --git a/chrome/browser/android/ntp/content_suggestions_notifier_service.cc b/chrome/browser/android/ntp/content_suggestions_notifier_service.cc
index 4ec864e13df26d31bdd70aeb432e8c7c0a467f37..c58105de1f3e55e1e46db73ee1ec8d99ebd82539 100644
--- a/chrome/browser/android/ntp/content_suggestions_notifier_service.cc
+++ b/chrome/browser/android/ntp/content_suggestions_notifier_service.cc
@@ -8,6 +8,7 @@
 
 #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"
@@ -235,6 +236,9 @@ ContentSuggestionsNotifierService::ContentSuggestionsNotifierService(
     : profile_(profile), suggestions_service_(suggestions) {
   ContentSuggestionsNotificationHelper::FlushCachedMetrics();
   UpdateObserverRegistrationState();
+
+  UMA_HISTOGRAM_BOOLEAN("ContentSuggestions.Preferences.Notifications",
+                        IsEnabled());
 }
 
 ContentSuggestionsNotifierService::~ContentSuggestionsNotifierService() =