ntp_tiles: Avoid redundant calls to TopSites

components/ntp_tiles/most_visited_sites.cc

 // Copyright 2013 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_tiles/most_visited_sites.h"
 
 #include <algorithm>
 #include <set>
 #include <string>
 #include <utility>
@@ skipping 151 matching lines @@
   // Get the current suggestions from cache. If the cache is empty, this will
   // fall back to TopSites.
   OnSuggestionsProfileAvailable(
       suggestions_service_->GetSuggestionsDataFromCache().value_or(
           SuggestionsProfile()));
 }
 
 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()),
       false);
 }
 
 base::FilePath MostVisitedSites::GetWhitelistLargeIconPath(const GURL& url) {
   if (supervisor_) {
     for (const auto& whitelist : supervisor_->whitelists()) {
       if (AreURLsEquivalent(whitelist.entry_point, url))
@@ skipping 227 matching lines @@
 
 void MostVisitedSites::TopSitesChanged(TopSites* top_sites,
                                        ChangeReason change_reason) {
   if (mv_source_ == NTPTileSource::TOP_SITES) {
     // The displayed tiles are invalidated.
     InitiateTopSitesQuery();
   }
 }
 
 }  // namespace ntp_tiles