[NTP Snippets] Limit the number of snippets to 10

components/ntp_snippets/ntp_snippets_service.cc

 // 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 "components/ntp_snippets/ntp_snippets_service.h"
 
 #include <algorithm>
 #include <iterator>
 #include <utility>
 
@@ skipping 15 matching lines @@
 #include "components/suggestions/proto/suggestions.pb.h"
 
 using suggestions::ChromeSuggestion;
 using suggestions::SuggestionsProfile;
 using suggestions::SuggestionsService;
 
 namespace ntp_snippets {
 
 namespace {
 
+const int kMaxSnippetCount = 10;
+
 const int kFetchingIntervalWifiChargingSeconds = 30 * 60;
 const int kFetchingIntervalWifiSeconds = 2 * 60 * 60;
 const int kFetchingIntervalFallbackSeconds = 24 * 60 * 60;
 
 // These define the times of day during which we will fetch via Wifi (without
 // charging) - 6 AM to 10 PM.
 const int kWifiFetchingHourMin = 6;
 const int kWifiFetchingHourMax = 22;
 
 const int kDefaultExpiryTimeMins = 24 * 60;
@@ skipping 182 matching lines @@
 }
 
 void NTPSnippetsService::FetchSnippets() {
   FetchSnippetsFromHosts(GetSuggestionsHosts());
 }
 
 void NTPSnippetsService::FetchSnippetsFromHosts(
     const std::set<std::string>& hosts) {
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kDontRestrict)) {
-    snippets_fetcher_->FetchSnippets(std::set<std::string>());
+    snippets_fetcher_->FetchSnippets(std::set<std::string>(), kMaxSnippetCount);
     return;
   }
   if (!hosts.empty()) {
-    snippets_fetcher_->FetchSnippets(hosts);
+    snippets_fetcher_->FetchSnippets(hosts, kMaxSnippetCount);
   } else {
     last_fetch_status_ = kStatusMessageEmptyHosts;
     LoadingSnippetsFinished();
   }
 }
 
 void NTPSnippetsService::RescheduleFetching() {
   // The scheduler only exists on Android so far, it's null on other platforms.
   if (!scheduler_)
     return;
@@ skipping 50 matching lines @@
 }
 
 void NTPSnippetsService::AddObserver(NTPSnippetsServiceObserver* observer) {
   observers_.AddObserver(observer);
 }
 
 void NTPSnippetsService::RemoveObserver(NTPSnippetsServiceObserver* observer) {
   observers_.RemoveObserver(observer);
 }
 
+// static
+int NTPSnippetsService::GetMaxSnippetCountForTesting() {
+  return kMaxSnippetCount;
+}
+
 void NTPSnippetsService::OnSuggestionsChanged(
     const SuggestionsProfile& suggestions) {
   std::set<std::string> hosts = GetSuggestionsHostsImpl(suggestions);
   if (hosts == GetSnippetHostsFromPrefs())
     return;
 
   // Remove existing snippets that aren't in the suggestions anymore.
   snippets_.erase(
       std::remove_if(snippets_.begin(), snippets_.end(),
                      [&hosts](const scoped_ptr<NTPSnippet>& snippet) {
@@ skipping 84 matching lines @@
           snippet->publish_date() +
           base::TimeDelta::FromMinutes(kDefaultExpiryTimeMins));
     }
   }
 
   // Insert the new snippets at the front.
   snippets_.insert(snippets_.begin(),
                    std::make_move_iterator(new_snippets.begin()),
                    std::make_move_iterator(new_snippets.end()));
 
+  // If there are more snippets now than we want to show, drop the extra ones
+  // from the end of the list.
+  if (snippets_.size() > kMaxSnippetCount)
+    snippets_.resize(kMaxSnippetCount);
+
   return true;
 }
 
 void NTPSnippetsService::LoadSnippetsFromPrefs() {
   bool success = LoadFromListValue(*pref_service_->GetList(prefs::kSnippets));
   DCHECK(success) << "Failed to parse snippets from prefs";
 
   LoadingSnippetsFinished();
 }
 
@@ skipping 70 matching lines @@
     if (snippet->expiry_date() < next_expiry)
       next_expiry = snippet->expiry_date();
   }
   DCHECK_GT(next_expiry, expiry);
   expiry_timer_.Start(FROM_HERE, next_expiry - expiry,
                       base::Bind(&NTPSnippetsService::LoadingSnippetsFinished,
                                  base::Unretained(this)));
 }
 
 }  // namespace ntp_snippets