Add UMA stats to allow computing the average size of the TopSites blacklist per user.

chrome/browser/history/top_sites_impl.cc

 // Copyright (c) 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/history/top_sites_impl.h"
 
 #include <algorithm>
 #include <set>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
+#include "base/metrics/histogram.h"
 #include "base/logging.h"
 #include "base/md5.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/prefs/pref_service.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/task_runner.h"
 #include "base/values.h"
 #include "chrome/browser/chrome_notification_types.h"
@@ skipping 662 matching lines @@
         IndexOf(*urls, prepopulate_urls[i].url) == -1) {
       urls->push_back(prepopulate_urls[i]);
       added = true;
     }
   }
   return added;
 }
 
 void TopSitesImpl::ApplyBlacklist(const MostVisitedURLList& urls,
                                   MostVisitedURLList* out) {
+  // Log the number of times ApplyBlacklist is called so we can compute the
+  // average number of blacklisted items per user.
+  const DictionaryValue* blacklist =
+      profile_->GetPrefs()->GetDictionary(prefs::kNtpMostVisitedURLsBlacklist);
+  UMA_HISTOGRAM_BOOLEAN("TopSites.NumberOfApplyBlacklist", true);
+  UMA_HISTOGRAM_COUNTS_100("TopSites.NumberOfBlacklistedItems",
+      (blacklist ? blacklist->size() : 0));
   for (size_t i = 0; i < urls.size() && i < kTopSitesNumber; ++i) {
     if (!IsBlacklisted(urls[i].url))
       out->push_back(urls[i]);
   }
 }
 
 std::string TopSitesImpl::GetURLHash(const GURL& url) {
   // We don't use canonical URLs here to be able to blacklist only one of
   // the two 'duplicate' sites, e.g. 'gmail.com' and 'mail.google.com'.
   return base::MD5String(url.spec());
@@ skipping 232 matching lines @@
   SetTopSites(pages);
 
   // Used only in testing.
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_TOP_SITES_UPDATED,
       content::Source<TopSitesImpl>(this),
       content::Details<CancelableRequestProvider::Handle>(&handle));
 }
 
 }  // namespace history