ntp_tiles: Add tests covering tile-fetching logic

components/ntp_tiles/most_visited_sites.cc

Index: components/ntp_tiles/most_visited_sites.cc
diff --git a/components/ntp_tiles/most_visited_sites.cc b/components/ntp_tiles/most_visited_sites.cc
index 35bfd4472236aa1aba96a84fc47eae3af3d16546..615cc9ab1d6832e49fceca612179a9c604b3a825 100644
--- a/components/ntp_tiles/most_visited_sites.cc
+++ b/components/ntp_tiles/most_visited_sites.cc
@@ -18,7 +18,7 @@
 #include "components/ntp_tiles/icon_cacher.h"
 #include "components/ntp_tiles/pref_names.h"
 #include "components/ntp_tiles/switches.h"
-#include "components/pref_registry/pref_registry_syncable.h"
+#include "components/prefs/pref_registry_simple.h"

[Marc Treib, 2016/12/19 09:11:50]

Nice! Once we do the same for PopularSites, we can probably remove the
dependency on components/pref_registry :)

[mastiz, 2017/01/09 10:40:58]

sfiera@ raised some concerns so I reverted this change :-/

 #include "components/prefs/pref_service.h"
 
 using history::TopSites;
@@ -153,8 +153,7 @@ void MostVisitedSites::OnBlockedSitesChanged() {
 }
 
 // static
-void MostVisitedSites::RegisterProfilePrefs(
-    user_prefs::PrefRegistrySyncable* registry) {
+void MostVisitedSites::RegisterProfilePrefs(PrefRegistrySimple* registry) {
   registry->RegisterIntegerPref(prefs::kNumPersonalTiles, 0);
 }
 
@@ -187,6 +186,8 @@ base::FilePath MostVisitedSites::GetWhitelistLargeIconPath(const GURL& url) {
 
 void MostVisitedSites::OnMostVisitedURLsAvailable(
     const history::MostVisitedURLList& visited_list) {
+  // TODO(mastiz): Verify if suggestion service results have been fetched in
+  // the meantime, and if that's the case ignore this event.
   NTPTilesVector tiles;
   size_t num_tiles =
       std::min(visited_list.size(), static_cast<size_t>(num_sites_));