Android NTP: only query TopSites if SuggestionsService has nothing in the cache

chrome/browser/android/ntp/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 "chrome/browser/android/ntp/most_visited_sites.h"
 
 #include <utility>
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_array.h"
@@ skipping 219 matching lines @@
         profile_,
         GetPopularSitesCountry(),
         GetPopularSitesVersion(),
         false,
         base::Bind(&MostVisitedSites::OnPopularSitesAvailable,
                    base::Unretained(this))));
   } else {
     received_popular_sites_ = true;
   }
 
+  SuggestionsService* suggestions_service =
+      SuggestionsServiceFactory::GetForProfile(profile_);
+  // Immediately get the current suggestions from the cache. If the cache is
+  // empty, this will fall back to TopSites.
   OnSuggestionsProfileAvailable(
-      SuggestionsServiceFactory::GetForProfile(profile_)
-          ->GetSuggestionsDataFromCache());
-
-  QueryMostVisitedURLs();
+      suggestions_service->GetSuggestionsDataFromCache());
+  // Also start a request for fresh suggestions.
+  suggestions_service->FetchSuggestionsData();
 
   scoped_refptr<TopSites> top_sites = TopSitesFactory::GetForProfile(profile_);
   if (top_sites) {
     // TopSites updates itself after a delay. To ensure up-to-date results,
     // force an update now.
     top_sites->SyncWithHistory();
 
     // Register as TopSitesObserver so that we can update ourselves when the
     // TopSites changes.
     scoped_observer_.Add(top_sites.get());
@@ skipping 156 matching lines @@
 // static
 void MostVisitedSites::RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
   registry->RegisterListPref(prefs::kNTPSuggestionsURL);
   registry->RegisterListPref(prefs::kNTPSuggestionsIsPersonal);
 }
 
 void MostVisitedSites::QueryMostVisitedURLs() {
   SuggestionsService* suggestions_service =
       SuggestionsServiceFactory::GetForProfile(profile_);
-  if (!suggestions_service->FetchSuggestionsData())

[Marc Treib, 2016/03/31 12:26:03]

What happened before is:
This got called from SetMostVisitedURLsObserver above, after we had fetched the
cached suggestions.
suggestions_service->FetchSuggestionsData would return false ("No, I didn't send
a network request, because I don't know yet if History Sync is enabled"), so
we'd fall back to TopSites, which would overwrite our cached suggestions.

-    InitiateTopSitesQuery();
+  if (suggestions_service->FetchSuggestionsData()) {
+    // A suggestions network request is on its way. We'll be called back via
+    // OnSuggestionsProfileAvailable.
+    return;
+  }
+  // If no network request could be sent, try to get suggestions from the
+  // cache. If that also returns nothing, OnSuggestionsProfileAvailable will
+  // call InitiateTopSitesQuery.
+  OnSuggestionsProfileAvailable(
+      suggestions_service->GetSuggestionsDataFromCache());
 }
 
 void MostVisitedSites::InitiateTopSitesQuery() {
   scoped_refptr<TopSites> top_sites = TopSitesFactory::GetForProfile(profile_);
   if (!top_sites)
     return;
 
   top_sites->GetMostVisitedURLs(
       base::Bind(&MostVisitedSites::OnMostVisitedURLsAvailable,
                  weak_ptr_factory_.GetWeakPtr()),
@@ skipping 426 matching lines @@
   }
 }
 
 static jlong Init(JNIEnv* env,
                   const JavaParamRef<jobject>& obj,
                   const JavaParamRef<jobject>& jprofile) {
   MostVisitedSites* most_visited_sites =
       new MostVisitedSites(ProfileAndroid::FromProfileAndroid(jprofile));
   return reinterpret_cast<intptr_t>(most_visited_sites);
 }