chrome/browser/predictors/autocomplete_action_predictor.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chrome/browser/predictors/autocomplete_action_predictor.h"
   6
   7 #include <math.h>
   8
   9 #include <vector>
  10
  11 #include "base/bind.h"
  12 #include "base/guid.h"
  13 #include "base/i18n/case_conversion.h"
  14 #include "base/metrics/histogram.h"
  15 #include "base/strings/string_util.h"
  16 #include "base/strings/stringprintf.h"
  17 #include "base/strings/utf_string_conversions.h"
  18 #include "chrome/browser/autocomplete/autocomplete_match.h"
  19 #include "chrome/browser/autocomplete/autocomplete_result.h"
  20 #include "chrome/browser/chrome_notification_types.h"
  21 #include "chrome/browser/history/history_notifications.h"
  22 #include "chrome/browser/history/history_service.h"
  23 #include "chrome/browser/history/history_service_factory.h"
  24 #include "chrome/browser/history/in_memory_database.h"
  25 #include "chrome/browser/omnibox/omnibox_log.h"
  26 #include "chrome/browser/predictors/autocomplete_action_predictor_factory.h"
  27 #include "chrome/browser/predictors/predictor_database.h"
  28 #include "chrome/browser/predictors/predictor_database_factory.h"
  29 #include "chrome/browser/prerender/prerender_field_trial.h"
  30 #include "chrome/browser/prerender/prerender_handle.h"
  31 #include "chrome/browser/prerender/prerender_manager.h"
  32 #include "chrome/browser/prerender/prerender_manager_factory.h"
  33 #include "chrome/browser/profiles/profile.h"
  34 #include "chrome/browser/ui/omnibox/omnibox_popup_model.h"
  35 #include "content/public/browser/browser_thread.h"
  36 #include "content/public/browser/notification_details.h"
  37 #include "content/public/browser/notification_service.h"
  38 #include "content/public/browser/notification_source.h"
  39
  40 namespace {
  41
  42 const float kConfidenceCutoff[] = {
  43   0.8f,
  44   0.5f
  45 };
  46
  47 COMPILE_ASSERT(arraysize(kConfidenceCutoff) ==
  48                predictors::AutocompleteActionPredictor::LAST_PREDICT_ACTION,
  49                ConfidenceCutoff_count_mismatch);
  50
  51 const size_t kMinimumUserTextLength = 1;
  52 const int kMinimumNumberOfHits = 3;
  53
  54 enum DatabaseAction {
  55   DATABASE_ACTION_ADD,
  56   DATABASE_ACTION_UPDATE,
  57   DATABASE_ACTION_DELETE_SOME,
  58   DATABASE_ACTION_DELETE_ALL,
  59   DATABASE_ACTION_COUNT
  60 };
  61
  62 }  // namespace
  63
  64 namespace predictors {
  65
  66 const int AutocompleteActionPredictor::kMaximumDaysToKeepEntry = 14;
  67
  68 AutocompleteActionPredictor::AutocompleteActionPredictor(Profile* profile)
  69     : profile_(profile),
  70       main_profile_predictor_(NULL),
  71       incognito_predictor_(NULL),
  72       initialized_(false) {
  73   if (profile_->IsOffTheRecord()) {
  74     main_profile_predictor_ = AutocompleteActionPredictorFactory::GetForProfile(
  75         profile_->GetOriginalProfile());
  76     DCHECK(main_profile_predictor_);
  77     main_profile_predictor_->incognito_predictor_ = this;
  78     if (main_profile_predictor_->initialized_)
  79       CopyFromMainProfile();
  80   } else {
  81     // Request the in-memory database from the history to force it to load so
  82     // it's available as soon as possible.
  83     HistoryService* history_service = HistoryServiceFactory::GetForProfile(
  84         profile_, Profile::EXPLICIT_ACCESS);
  85     if (history_service)
  86       history_service->InMemoryDatabase();
  87
  88     table_ =
  89         PredictorDatabaseFactory::GetForProfile(profile_)->autocomplete_table();
  90
  91     // Observe all main frame loads so we can wait for the first to complete
  92     // before accessing DB and IO threads to build the local cache.
  93     notification_registrar_.Add(this,
  94                                 content::NOTIFICATION_LOAD_COMPLETED_MAIN_FRAME,
  95                                 content::NotificationService::AllSources());
  96   }
  97 }
  98
  99 AutocompleteActionPredictor::~AutocompleteActionPredictor() {
 100   if (main_profile_predictor_)
 101     main_profile_predictor_->incognito_predictor_ = NULL;
 102   else if (incognito_predictor_)
 103     incognito_predictor_->main_profile_predictor_ = NULL;
 104   if (prerender_handle_.get())
 105     prerender_handle_->OnCancel();
 106 }
 107
 108 void AutocompleteActionPredictor::RegisterTransitionalMatches(
 109     const base::string16& user_text,
 110     const AutocompleteResult& result) {
 111   if (user_text.length() < kMinimumUserTextLength)
 112     return;
 113   const base::string16 lower_user_text(base::i18n::ToLower(user_text));
 114
 115   // Merge this in to an existing match if we already saw |user_text|
 116   std::vector<TransitionalMatch>::iterator match_it =
 117       std::find(transitional_matches_.begin(), transitional_matches_.end(),
 118                 lower_user_text);
 119
 120   if (match_it == transitional_matches_.end()) {
 121     TransitionalMatch transitional_match;
 122     transitional_match.user_text = lower_user_text;
 123     match_it = transitional_matches_.insert(transitional_matches_.end(),
 124                                             transitional_match);
 125   }
 126
 127   for (AutocompleteResult::const_iterator i(result.begin()); i != result.end();
 128        ++i) {
 129     if (std::find(match_it->urls.begin(), match_it->urls.end(),
 130                   i->destination_url) == match_it->urls.end()) {
 131       match_it->urls.push_back(i->destination_url);
 132     }
 133   }
 134 }
 135
 136 void AutocompleteActionPredictor::ClearTransitionalMatches() {
 137   transitional_matches_.clear();
 138 }
 139
 140 void AutocompleteActionPredictor::CancelPrerender() {
 141   // If the prerender has already been abandoned, leave it to its own timeout;
 142   // this normally gets called immediately after OnOmniboxOpenedUrl.
 143   if (prerender_handle_ && !prerender_handle_->IsAbandoned()) {
 144     prerender_handle_->OnCancel();
 145     prerender_handle_.reset();
 146   }
 147 }
 148
 149 void AutocompleteActionPredictor::StartPrerendering(
 150     const GURL& url,
 151     const content::SessionStorageNamespaceMap& session_storage_namespace_map,
 152     const gfx::Size& size) {
 153   // Only cancel the old prerender after starting the new one, so if the URLs
 154   // are the same, the underlying prerender will be reused.
 155   scoped_ptr<prerender::PrerenderHandle> old_prerender_handle(
 156       prerender_handle_.release());
 157   if (prerender::PrerenderManager* prerender_manager =
 158           prerender::PrerenderManagerFactory::GetForProfile(profile_)) {
 159     content::SessionStorageNamespace* session_storage_namespace = NULL;
 160     content::SessionStorageNamespaceMap::const_iterator it =
 161         session_storage_namespace_map.find(std::string());
 162     if (it != session_storage_namespace_map.end())
 163       session_storage_namespace = it->second.get();
 164     prerender_handle_.reset(prerender_manager->AddPrerenderFromOmnibox(
 165         url, session_storage_namespace, size));
 166   }
 167   if (old_prerender_handle)
 168     old_prerender_handle->OnCancel();
 169 }
 170
 171 // Given a match, return a recommended action.
 172 AutocompleteActionPredictor::Action
 173     AutocompleteActionPredictor::RecommendAction(
 174         const base::string16& user_text,
 175         const AutocompleteMatch& match) const {
 176   bool is_in_db = false;
 177   const double confidence = CalculateConfidence(user_text, match, &is_in_db);
 178   DCHECK(confidence >= 0.0 && confidence <= 1.0);
 179
 180   UMA_HISTOGRAM_BOOLEAN("AutocompleteActionPredictor.MatchIsInDb", is_in_db);
 181
 182   if (is_in_db) {
 183     // Multiple enties with the same URL are fine as the confidence may be
 184     // different.
 185     tracked_urls_.push_back(std::make_pair(match.destination_url, confidence));
 186     UMA_HISTOGRAM_COUNTS_100("AutocompleteActionPredictor.Confidence",
 187                              confidence * 100);
 188   }
 189
 190   // Map the confidence to an action.
 191   Action action = ACTION_NONE;
 192   for (int i = 0; i < LAST_PREDICT_ACTION; ++i) {
 193     if (confidence >= kConfidenceCutoff[i]) {
 194       action = static_cast<Action>(i);
 195       break;
 196     }
 197   }
 198
 199   // Downgrade prerender to preconnect if this is a search match or if omnibox
 200   // prerendering is disabled. There are cases when Instant will not handle a
 201   // search suggestion and in those cases it would be good to prerender the
 202   // search results, however search engines have not been set up to correctly
 203   // handle being prerendered and until they are we should avoid it.
 204   // http://crbug.com/117495
 205   if (action == ACTION_PRERENDER &&
 206       (AutocompleteMatch::IsSearchType(match.type) ||
 207        !prerender::IsOmniboxEnabled(profile_))) {
 208     action = ACTION_PRECONNECT;
 209   }
 210
 211   return action;
 212 }
 213
 214 // Return true if the suggestion type warrants a TCP/IP preconnection.
 215 // i.e., it is now quite likely that the user will select the related domain.
 216 // static
 217 bool AutocompleteActionPredictor::IsPreconnectable(
 218     const AutocompleteMatch& match) {
 219   return AutocompleteMatch::IsSearchType(match.type);
 220 }
 221
 222 bool AutocompleteActionPredictor::IsPrerenderAbandonedForTesting() {
 223   return prerender_handle_ && prerender_handle_->IsAbandoned();
 224 }
 225
 226 void AutocompleteActionPredictor::Observe(
 227     int type,
 228     const content::NotificationSource& source,
 229     const content::NotificationDetails& details) {
 230   switch (type) {
 231     case content::NOTIFICATION_LOAD_COMPLETED_MAIN_FRAME:
 232       CreateLocalCachesFromDatabase();
 233       notification_registrar_.Remove(
 234           this,
 235           content::NOTIFICATION_LOAD_COMPLETED_MAIN_FRAME,
 236           content::NotificationService::AllSources());
 237       break;
 238
 239     case chrome::NOTIFICATION_HISTORY_URLS_DELETED: {
 240       DCHECK(initialized_);
 241       const content::Details<const history::URLsDeletedDetails>
 242           urls_deleted_details =
 243               content::Details<const history::URLsDeletedDetails>(details);
 244       if (urls_deleted_details->all_history)
 245         DeleteAllRows();
 246       else
 247         DeleteRowsWithURLs(urls_deleted_details->rows);
 248       break;
 249     }
 250
 251     case chrome::NOTIFICATION_OMNIBOX_OPENED_URL: {
 252       DCHECK(initialized_);
 253
 254       // TODO(dominich): This doesn't need to be synchronous. Investigate
 255       // posting it as a task to be run later.
 256       OnOmniboxOpenedUrl(*content::Details<OmniboxLog>(details).ptr());
 257       break;
 258     }
 259
 260     case chrome::NOTIFICATION_HISTORY_LOADED: {
 261       TryDeleteOldEntries(content::Details<HistoryService>(details).ptr());
 262
 263       notification_registrar_.Remove(this,
 264                                      chrome::NOTIFICATION_HISTORY_LOADED,
 265                                      content::Source<Profile>(profile_));
 266       break;
 267     }
 268
 269     default:
 270       NOTREACHED() << "Unexpected notification observed.";
 271       break;
 272   }
 273 }
 274
 275 void AutocompleteActionPredictor::CreateLocalCachesFromDatabase() {
 276   // Create local caches using the database as loaded. We will garbage collect
 277   // rows from the caches and the database once the history service is
 278   // available.
 279   std::vector<AutocompleteActionPredictorTable::Row>* rows =
 280       new std::vector<AutocompleteActionPredictorTable::Row>();
 281   content::BrowserThread::PostTaskAndReply(content::BrowserThread::DB,
 282       FROM_HERE,
 283       base::Bind(&AutocompleteActionPredictorTable::GetAllRows, table_, rows),
 284       base::Bind(&AutocompleteActionPredictor::CreateCaches, AsWeakPtr(),
 285                  base::Owned(rows)));
 286 }
 287
 288 void AutocompleteActionPredictor::DeleteAllRows() {
 289   if (!initialized_)
 290     return;
 291
 292   db_cache_.clear();
 293   db_id_cache_.clear();
 294
 295   if (table_.get()) {
 296     content::BrowserThread::PostTask(content::BrowserThread::DB, FROM_HERE,
 297         base::Bind(&AutocompleteActionPredictorTable::DeleteAllRows,
 298                    table_));
 299   }
 300
 301   UMA_HISTOGRAM_ENUMERATION("AutocompleteActionPredictor.DatabaseAction",
 302                             DATABASE_ACTION_DELETE_ALL, DATABASE_ACTION_COUNT);
 303 }
 304
 305 void AutocompleteActionPredictor::DeleteRowsWithURLs(
 306     const history::URLRows& rows) {
 307   if (!initialized_)
 308     return;
 309
 310   std::vector<AutocompleteActionPredictorTable::Row::Id> id_list;
 311
 312   for (DBCacheMap::iterator it = db_cache_.begin(); it != db_cache_.end();) {
 313     if (std::find_if(rows.begin(), rows.end(),
 314         history::URLRow::URLRowHasURL(it->first.url)) != rows.end()) {
 315       const DBIdCacheMap::iterator id_it = db_id_cache_.find(it->first);
 316       DCHECK(id_it != db_id_cache_.end());
 317       id_list.push_back(id_it->second);
 318       db_id_cache_.erase(id_it);
 319       db_cache_.erase(it++);
 320     } else {
 321       ++it;
 322     }
 323   }
 324
 325   if (table_.get()) {
 326     content::BrowserThread::PostTask(content::BrowserThread::DB, FROM_HERE,
 327         base::Bind(&AutocompleteActionPredictorTable::DeleteRows, table_,
 328                    id_list));
 329   }
 330
 331   UMA_HISTOGRAM_ENUMERATION("AutocompleteActionPredictor.DatabaseAction",
 332                             DATABASE_ACTION_DELETE_SOME, DATABASE_ACTION_COUNT);
 333 }
 334
 335 void AutocompleteActionPredictor::OnOmniboxOpenedUrl(const OmniboxLog& log) {
 336   if (log.text.length() < kMinimumUserTextLength)
 337     return;
 338
 339   // Do not attempt to learn from omnibox interactions where the omnibox
 340   // dropdown is closed.  In these cases the user text (|log.text|) that we
 341   // learn from is either empty or effectively identical to the destination
 342   // string.  In either case, it can't teach us much.  Also do not attempt
 343   // to learn from paste-and-go actions even if the popup is open because
 344   // the paste-and-go destination has no relation to whatever text the user
 345   // may have typed.
 346   if (!log.is_popup_open || log.is_paste_and_go)
 347     return;
 348
 349   // Abandon the current prerender. If it is to be used, it will be used very
 350   // soon, so use the lower timeout.
 351   if (prerender_handle_) {
 352     prerender_handle_->OnNavigateAway();
 353     // Don't release |prerender_handle_| so it is canceled if it survives to the
 354     // next StartPrerendering call.
 355   }
 356
 357   UMA_HISTOGRAM_BOOLEAN(
 358       base::StringPrintf("Prerender.OmniboxNavigationsCouldPrerender%s",
 359                          prerender::PrerenderManager::GetModeString()).c_str(),
 360       prerender::IsOmniboxEnabled(profile_));
 361
 362   const AutocompleteMatch& match = log.result.match_at(log.selected_index);
 363   const GURL& opened_url = match.destination_url;
 364   const base::string16 lower_user_text(base::i18n::ToLower(log.text));
 365
 366   // Traverse transitional matches for those that have a user_text that is a
 367   // prefix of |lower_user_text|.
 368   std::vector<AutocompleteActionPredictorTable::Row> rows_to_add;
 369   std::vector<AutocompleteActionPredictorTable::Row> rows_to_update;
 370
 371   for (std::vector<TransitionalMatch>::const_iterator it =
 372         transitional_matches_.begin(); it != transitional_matches_.end();
 373         ++it) {
 374     if (!StartsWith(lower_user_text, it->user_text, true))
 375       continue;
 376
 377     // Add entries to the database for those matches.
 378     for (std::vector<GURL>::const_iterator url_it = it->urls.begin();
 379           url_it != it->urls.end(); ++url_it) {
 380       DCHECK(it->user_text.length() >= kMinimumUserTextLength);
 381       const DBCacheKey key = { it->user_text, *url_it };
 382       const bool is_hit = (*url_it == opened_url);
 383
 384       AutocompleteActionPredictorTable::Row row;
 385       row.user_text = key.user_text;
 386       row.url = key.url;
 387
 388       DBCacheMap::iterator it = db_cache_.find(key);
 389       if (it == db_cache_.end()) {
 390         row.id = base::GenerateGUID();
 391         row.number_of_hits = is_hit ? 1 : 0;
 392         row.number_of_misses = is_hit ? 0 : 1;
 393
 394         rows_to_add.push_back(row);
 395       } else {
 396         DCHECK(db_id_cache_.find(key) != db_id_cache_.end());
 397         row.id = db_id_cache_.find(key)->second;
 398         row.number_of_hits = it->second.number_of_hits + (is_hit ? 1 : 0);
 399         row.number_of_misses = it->second.number_of_misses + (is_hit ? 0 : 1);
 400
 401         rows_to_update.push_back(row);
 402       }
 403     }
 404   }
 405   if (rows_to_add.size() > 0 || rows_to_update.size() > 0)
 406     AddAndUpdateRows(rows_to_add, rows_to_update);
 407
 408   ClearTransitionalMatches();
 409
 410   // Check against tracked urls and log accuracy for the confidence we
 411   // predicted.
 412   for (std::vector<std::pair<GURL, double> >::const_iterator it =
 413        tracked_urls_.begin(); it != tracked_urls_.end();
 414        ++it) {
 415     if (opened_url == it->first) {
 416       UMA_HISTOGRAM_COUNTS_100("AutocompleteActionPredictor.AccurateCount",
 417                                it->second * 100);
 418     }
 419   }
 420   tracked_urls_.clear();
 421 }
 422
 423 void AutocompleteActionPredictor::AddAndUpdateRows(
 424     const AutocompleteActionPredictorTable::Rows& rows_to_add,
 425     const AutocompleteActionPredictorTable::Rows& rows_to_update) {
 426   if (!initialized_)
 427     return;
 428
 429   for (AutocompleteActionPredictorTable::Rows::const_iterator it =
 430        rows_to_add.begin(); it != rows_to_add.end(); ++it) {
 431     const DBCacheKey key = { it->user_text, it->url };
 432     DBCacheValue value = { it->number_of_hits, it->number_of_misses };
 433
 434     DCHECK(db_cache_.find(key) == db_cache_.end());
 435
 436     db_cache_[key] = value;
 437     db_id_cache_[key] = it->id;
 438     UMA_HISTOGRAM_ENUMERATION("AutocompleteActionPredictor.DatabaseAction",
 439                               DATABASE_ACTION_ADD, DATABASE_ACTION_COUNT);
 440   }
 441   for (AutocompleteActionPredictorTable::Rows::const_iterator it =
 442        rows_to_update.begin(); it != rows_to_update.end(); ++it) {
 443     const DBCacheKey key = { it->user_text, it->url };
 444
 445     DBCacheMap::iterator db_it = db_cache_.find(key);
 446     DCHECK(db_it != db_cache_.end());
 447     DCHECK(db_id_cache_.find(key) != db_id_cache_.end());
 448
 449     db_it->second.number_of_hits = it->number_of_hits;
 450     db_it->second.number_of_misses = it->number_of_misses;
 451     UMA_HISTOGRAM_ENUMERATION("AutocompleteActionPredictor.DatabaseAction",
 452                               DATABASE_ACTION_UPDATE, DATABASE_ACTION_COUNT);
 453   }
 454
 455   if (table_.get()) {
 456     content::BrowserThread::PostTask(content::BrowserThread::DB, FROM_HERE,
 457         base::Bind(&AutocompleteActionPredictorTable::AddAndUpdateRows,
 458                    table_, rows_to_add, rows_to_update));
 459   }
 460 }
 461
 462 void AutocompleteActionPredictor::CreateCaches(
 463     std::vector<AutocompleteActionPredictorTable::Row>* rows) {
 464   CHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 465   DCHECK(!profile_->IsOffTheRecord());
 466   DCHECK(!initialized_);
 467   DCHECK(db_cache_.empty());
 468   DCHECK(db_id_cache_.empty());
 469
 470   for (std::vector<AutocompleteActionPredictorTable::Row>::const_iterator it =
 471        rows->begin(); it != rows->end(); ++it) {
 472     const DBCacheKey key = { it->user_text, it->url };
 473     const DBCacheValue value = { it->number_of_hits, it->number_of_misses };
 474     db_cache_[key] = value;
 475     db_id_cache_[key] = it->id;
 476   }
 477
 478   // If the history service is ready, delete any old or invalid entries.
 479   HistoryService* history_service =
 480       HistoryServiceFactory::GetForProfile(profile_, Profile::EXPLICIT_ACCESS);
 481   if (!TryDeleteOldEntries(history_service)) {
 482     // Wait for the notification that the history service is ready and the URL
 483     // DB is loaded.
 484     notification_registrar_.Add(this, chrome::NOTIFICATION_HISTORY_LOADED,
 485                                 content::Source<Profile>(profile_));
 486   }
 487 }
 488
 489 bool AutocompleteActionPredictor::TryDeleteOldEntries(HistoryService* service) {
 490   CHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 491   DCHECK(!profile_->IsOffTheRecord());
 492   DCHECK(!initialized_);
 493
 494   if (!service)
 495     return false;
 496
 497   history::URLDatabase* url_db = service->InMemoryDatabase();
 498   if (!url_db)
 499     return false;
 500
 501   DeleteOldEntries(url_db);
 502   return true;
 503 }
 504
 505 void AutocompleteActionPredictor::DeleteOldEntries(
 506     history::URLDatabase* url_db) {
 507   CHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 508   DCHECK(!profile_->IsOffTheRecord());
 509   DCHECK(!initialized_);
 510   DCHECK(table_.get());
 511
 512   std::vector<AutocompleteActionPredictorTable::Row::Id> ids_to_delete;
 513   DeleteOldIdsFromCaches(url_db, &ids_to_delete);
 514
 515   content::BrowserThread::PostTask(content::BrowserThread::DB, FROM_HERE,
 516       base::Bind(&AutocompleteActionPredictorTable::DeleteRows, table_,
 517                  ids_to_delete));
 518
 519   FinishInitialization();
 520   if (incognito_predictor_)
 521     incognito_predictor_->CopyFromMainProfile();
 522 }
 523
 524 void AutocompleteActionPredictor::DeleteOldIdsFromCaches(
 525     history::URLDatabase* url_db,
 526     std::vector<AutocompleteActionPredictorTable::Row::Id>* id_list) {
 527   CHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 528   DCHECK(!profile_->IsOffTheRecord());
 529   DCHECK(!initialized_);
 530   DCHECK(url_db);
 531   DCHECK(id_list);
 532
 533   id_list->clear();
 534   for (DBCacheMap::iterator it = db_cache_.begin(); it != db_cache_.end();) {
 535     history::URLRow url_row;
 536
 537     if ((url_db->GetRowForURL(it->first.url, &url_row) == 0) ||
 538         ((base::Time::Now() - url_row.last_visit()).InDays() >
 539          kMaximumDaysToKeepEntry)) {
 540       const DBIdCacheMap::iterator id_it = db_id_cache_.find(it->first);
 541       DCHECK(id_it != db_id_cache_.end());
 542       id_list->push_back(id_it->second);
 543       db_id_cache_.erase(id_it);
 544       db_cache_.erase(it++);
 545     } else {
 546       ++it;
 547     }
 548   }
 549 }
 550
 551 void AutocompleteActionPredictor::CopyFromMainProfile() {
 552   CHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 553   DCHECK(profile_->IsOffTheRecord());
 554   DCHECK(!initialized_);
 555   DCHECK(main_profile_predictor_);
 556   DCHECK(main_profile_predictor_->initialized_);
 557
 558   db_cache_ = main_profile_predictor_->db_cache_;
 559   db_id_cache_ = main_profile_predictor_->db_id_cache_;
 560   FinishInitialization();
 561 }
 562
 563 void AutocompleteActionPredictor::FinishInitialization() {
 564   CHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 565   DCHECK(!initialized_);
 566
 567   // Incognito and normal profiles should listen only to omnibox notifications
 568   // from their own profile, but both should listen to history deletions from
 569   // the main profile, since opening the history page in either case actually
 570   // opens the non-incognito history (and lets users delete from there).
 571   notification_registrar_.Add(this, chrome::NOTIFICATION_OMNIBOX_OPENED_URL,
 572                               content::Source<Profile>(profile_));
 573   notification_registrar_.Add(this, chrome::NOTIFICATION_HISTORY_URLS_DELETED,
 574       content::Source<Profile>(profile_->GetOriginalProfile()));
 575   initialized_ = true;
 576 }
 577
 578 double AutocompleteActionPredictor::CalculateConfidence(
 579     const base::string16& user_text,
 580     const AutocompleteMatch& match,
 581     bool* is_in_db) const {
 582   const DBCacheKey key = { user_text, match.destination_url };
 583
 584   *is_in_db = false;
 585   if (user_text.length() < kMinimumUserTextLength)
 586     return 0.0;
 587
 588   const DBCacheMap::const_iterator iter = db_cache_.find(key);
 589   if (iter == db_cache_.end())
 590     return 0.0;
 591
 592   *is_in_db = true;
 593   return CalculateConfidenceForDbEntry(iter);
 594 }
 595
 596 double AutocompleteActionPredictor::CalculateConfidenceForDbEntry(
 597     DBCacheMap::const_iterator iter) const {
 598   const DBCacheValue& value = iter->second;
 599   if (value.number_of_hits < kMinimumNumberOfHits)
 600     return 0.0;
 601
 602   const double number_of_hits = static_cast<double>(value.number_of_hits);
 603   return number_of_hits / (number_of_hits + value.number_of_misses);
 604 }
 605
 606 AutocompleteActionPredictor::TransitionalMatch::TransitionalMatch() {
 607 }
 608
 609 AutocompleteActionPredictor::TransitionalMatch::~TransitionalMatch() {
 610 }
 611
 612 }  // namespace predictors