Re-enable TopSites in PrerenderManager, this time duplicating the invariant

chrome/browser/history/top_sites.cc

 // Copyright (c) 2011 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/history/top_sites.h"
 
 #include <algorithm>
 #include <set>
 
 #include "base/logging.h"
@@ skipping 146 matching lines @@
                        prefs::kNTPMostVisitedURLsBlacklist).Get();
   DictionaryPrefUpdate(profile_->GetPrefs(),
                        prefs::kNTPMostVisitedPinnedURLs).Get();
 
   // Now the dictionaries are guaranteed to exist and we can cache pointers
   // to them.
   blacklist_ =
       profile_->GetPrefs()->GetDictionary(prefs::kNTPMostVisitedURLsBlacklist);
   pinned_urls_ =
       profile_->GetPrefs()->GetDictionary(prefs::kNTPMostVisitedPinnedURLs);
+  DCHECK(blacklist_ != NULL);
+  DCHECK(pinned_urls_ != NULL);
 }
 
 void TopSites::Init(const FilePath& db_name) {
   // Create the backend here, rather than in the constructor, so that
   // unit tests that do not need the backend can run without a problem.
   backend_ = new TopSitesBackend;
   backend_->Init(db_name);
   backend_->GetMostVisitedThumbnails(
       &top_sites_consumer_,
       NewCallback(this, &TopSites::OnGotMostVisitedThumbnails));
@@ skipping 829 matching lines @@
   SetTopSites(pages);
 
   // Used only in testing.
   NotificationService::current()->Notify(
       chrome::NOTIFICATION_TOP_SITES_UPDATED,
       Source<TopSites>(this),
       Details<CancelableRequestProvider::Handle>(&handle));
 }
 
 }  // namespace history