Adding a request counter to the snippets fetcher.

components/ntp_snippets/ntp_snippets_fetcher.cc

Index: components/ntp_snippets/ntp_snippets_fetcher.cc
diff --git a/components/ntp_snippets/ntp_snippets_fetcher.cc b/components/ntp_snippets/ntp_snippets_fetcher.cc
index 5869644f963492b331dfbcc2dc5eb70accf87db8..29d95325c0d7147a2ea4b7926a10c60081cc7d8f 100644
--- a/components/ntp_snippets/ntp_snippets_fetcher.cc
+++ b/components/ntp_snippets/ntp_snippets_fetcher.cc
@@ -76,6 +76,8 @@ const char kPersonalizationBothString[] = "both";  // the default value
 const char kHostRestrictionOnString[] = "on";  // the default value
 const char kHostRestrictionOffString[] = "off";
 
+const int kContentFetchesQuotaPerDay = 30;

[jkrcal, 2016/07/25 10:08:26]

I still wonder what is the right limit. I think 30 is more appropriate if we
keep updating every 30mins (when charging on wifi). Even with such a quota,
throttling could hit the user under normal conditions. Is there any strong
reason to update as often as every 30 mins?

[Marc Treib, 2016/07/25 10:11:55]

IMO regular users shouldn't hit the throttling limit - this is just a safeguard
against bad behavior. So maybe 50 for now?

[jkrcal, 2016/07/25 10:26:59]

Ok, changed to 50. Does fetching every 30 mins make sense?

[Marc Treib, 2016/07/25 11:07:46]

Probably not, but that's a separate discussion :)
For now, I'd like to keep the default values consistent at least.

[jkrcal, 2016/07/26 08:30:11]

Acknowledged.

+
 std::string FetchResultToString(NTPSnippetsFetcher::FetchResult result) {
   switch (result) {
     case NTPSnippetsFetcher::FetchResult::SUCCESS:
@@ -158,6 +160,7 @@ NTPSnippetsFetcher::NTPSnippetsFetcher(
     SigninManagerBase* signin_manager,
     OAuth2TokenService* token_service,
     scoped_refptr<URLRequestContextGetter> url_request_context_getter,
+    PrefService* pref_service,
     const ParseJSONCallback& parse_json_callback,
     bool is_stable_channel)
     : OAuth2TokenService::Consumer("ntp_snippets"),
@@ -172,6 +175,10 @@ NTPSnippetsFetcher::NTPSnippetsFetcher(
                      : CHROME_READER_API),
       is_stable_channel_(is_stable_channel),
       tick_clock_(new base::DefaultTickClock()),
+      request_throttler_(
+          pref_service,
+          RequestThrottler::RequestType::CONTENT_SUGGESTION_FETCHER,
+          kContentFetchesQuotaPerDay),
       weak_ptr_factory_(this) {
   // Parse the variation parameters and set the defaults if missing.
   std::string personalization = variations::GetVariationParamValue(
@@ -214,7 +221,11 @@ void NTPSnippetsFetcher::SetCallback(
 void NTPSnippetsFetcher::FetchSnippetsFromHosts(
     const std::set<std::string>& hosts,
     const std::string& language_code,
-    int count) {
+    int count,
+    bool force_request) {
+  if (!request_throttler_.DemandQuotaForRequest(force_request))
+    return;
+
   hosts_ = hosts;
   fetch_start_time_ = tick_clock_->NowTicks();