Cancel prerenders from Omnibox if we navigate to a different URL than predicted

chrome/browser/autocomplete/network_action_predictor.cc

 // Copyright (c) 2012 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/autocomplete/network_action_predictor.h"
 
 #include <math.h>
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/i18n/case_conversion.h"
 #include "base/metrics/histogram.h"
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/autocomplete/autocomplete.h"
 #include "chrome/browser/autocomplete/autocomplete_match.h"
 #include "chrome/browser/autocomplete/network_action_predictor_database.h"
 #include "chrome/browser/history/history.h"
 #include "chrome/browser/history/history_notifications.h"
 #include "chrome/browser/history/in_memory_database.h"
 #include "chrome/browser/prerender/prerender_field_trial.h"
+#include "chrome/browser/prerender/prerender_manager.h"
+#include "chrome/browser/prerender/prerender_manager_factory.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/guid.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_source.h"
 
 namespace {
 
@@ skipping 195 matching lines @@
   if (log.text.length() < kMinimumUserTextLength)
     return;
 
   const AutocompleteMatch& match = log.result.match_at(log.selected_index);
 
   UMA_HISTOGRAM_BOOLEAN("Prerender.OmniboxNavigationsCouldPrerender",
                         prerender::IsOmniboxEnabled(profile_));
 
   const GURL& opened_url = match.destination_url;
 
+  // If the Omnibox triggered a prerender but the URL doesn't match the one the
+  // user is navigating to, cancel the prerender.
+  prerender::PrerenderManager* prerender_manager =
+      prerender::PrerenderManagerFactory::GetForProfile(profile_);
+  // |prerender_manager| can be NULL in incognito mode or if prerendering is
+  // otherwise disabled.
+  if (prerender_manager && !prerender_manager->IsPrerendering(opened_url))
+    prerender_manager->CancelOmniboxPrerenders();
+
   const string16 lower_user_text(base::i18n::ToLower(log.text));
 
   BeginTransaction();
   // Traverse transitional matches for those that have a user_text that is a
   // prefix of |lower_user_text|.
   for (std::vector<TransitionalMatch>::const_iterator it =
        transitional_matches_.begin(); it != transitional_matches_.end();
        ++it) {
     if (!StartsWith(lower_user_text, it->user_text, true))
       continue;
@@ skipping 36 matching lines @@
        tracked_urls_.begin(); it != tracked_urls_.end();
        ++it) {
     if (opened_url == it->first) {
       UMA_HISTOGRAM_COUNTS_100("NetworkActionPredictor.AccurateCount",
                                it->second * 100);
     }
   }
   tracked_urls_.clear();
 }
 
-
 void NetworkActionPredictor::DeleteOldIdsFromCaches(
     history::URLDatabase* url_db,
     std::vector<NetworkActionPredictorDatabase::Row::Id>* id_list) {
   CHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   DCHECK(url_db);
   DCHECK(id_list);
   id_list->clear();
   for (DBCacheMap::iterator it = db_cache_.begin(); it != db_cache_.end();) {
     history::URLRow url_row;
 
@@ skipping 168 matching lines @@
 
   content::BrowserThread::PostTask(content::BrowserThread::DB, FROM_HERE,
       base::Bind(&NetworkActionPredictorDatabase::CommitTransaction, db_));
 }
 
 NetworkActionPredictor::TransitionalMatch::TransitionalMatch() {
 }
 
 NetworkActionPredictor::TransitionalMatch::~TransitionalMatch() {
 }