Make OnPopularURLsAvailable optional.

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 6917269cd739221b6e28799664b614187ea001db..814e3cfa94916c5b7412e31300eaf4eb5006400e 100644
--- a/components/ntp_tiles/most_visited_sites.cc
+++ b/components/ntp_tiles/most_visited_sites.cc
@@ -140,6 +140,9 @@ std::string GetSourceHistogramName(NTPTileSource source) {
 
 }  // namespace
 
+void MostVisitedSites::Observer::OnPopularURLsAvailable(
+    const PopularSitesVector& sites) {}

[Marc Treib, 2016/09/15 09:13:33]

Might as well put the empty body in the header. The dtor already does that.

[sfiera, 2016/09/21 08:35:26]

Done.

+
 MostVisitedSites::MostVisitedSites(PrefService* prefs,
                                    scoped_refptr<history::TopSites> top_sites,
                                    SuggestionsService* suggestions,