Introduce a request throttler for limiting requests in mobile NTP.

chrome/browser/prefs/browser_prefs.cc

Index: chrome/browser/prefs/browser_prefs.cc
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index c62343a7f64273890169048d4d1eda0d9a8dfe7f..b1d5ead6bffdeadfb4f23d504232e82bfa69b859 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -79,6 +79,7 @@
 #include "components/metrics/metrics_service.h"
 #include "components/network_time/network_time_tracker.h"
 #include "components/ntp_snippets/ntp_snippets_service.h"
+#include "components/ntp_snippets/request_counter.h"
 #include "components/omnibox/browser/zero_suggest_provider.h"
 #include "components/password_manager/core/browser/password_bubble_experiment.h"
 #include "components/password_manager/core/browser/password_manager.h"
@@ -461,6 +462,7 @@ void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry) {
   MediaStreamDevicesController::RegisterProfilePrefs(registry);
   NetPrefObserver::RegisterProfilePrefs(registry);
   ntp_snippets::NTPSnippetsService::RegisterProfilePrefs(registry);
+  ntp_snippets::RequestCounter::RegisterProfilePrefs(registry);
   password_bubble_experiment::RegisterPrefs(registry);
   password_manager::PasswordManager::RegisterProfilePrefs(registry);
   PrefProxyConfigTrackerImpl::RegisterProfilePrefs(registry);