ntp_tiles: Avoid redundant calls to TopSites

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 47918739aca14ab147eb3cd8b53317b70c7b1cef..f1d8d7b11bf01b483b8277a61762ac1ff5789fd5 100644
--- a/components/ntp_tiles/most_visited_sites.cc
+++ b/components/ntp_tiles/most_visited_sites.cc
@@ -169,6 +169,8 @@ void MostVisitedSites::BuildCurrentTiles() {
 void MostVisitedSites::InitiateTopSitesQuery() {
   if (!top_sites_)
     return;
+  if (weak_ptr_factory_.HasWeakPtrs())

[sfiera, 2016/12/16 16:15:03]

This seems brittle—it assumes we won't ever use weak pointers for anything but
top sites queries.

Can we add a bool outstanding_top_sites_query_ instead?

[mastiz, 2017/01/05 11:50:45]

You have a point, but adding yet another state variable looks as fragile to me
if not more.

What would you think of renaming to top_sites_weak_ptr_factor_? Not sure if this
violates a popular pattern.

+    return;  // Ongoing query.
   top_sites_->GetMostVisitedURLs(
       base::Bind(&MostVisitedSites::OnMostVisitedURLsAvailable,
                  weak_ptr_factory_.GetWeakPtr()),