Data from the autocomplete predictor wasn't deleted immediately when deleting browsing history.

chrome/browser/predictors/autocomplete_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/predictors/autocomplete_action_predictor.h"
 
 #include <math.h>
 #include <stddef.h>
 
 #include <vector>
@@ skipping 317 matching lines @@
   std::vector<AutocompleteActionPredictorTable::Row>* rows =
       new std::vector<AutocompleteActionPredictorTable::Row>();
   content::BrowserThread::PostTaskAndReply(
       content::BrowserThread::DB, FROM_HERE,
       base::Bind(&AutocompleteActionPredictorTable::GetAllRows, table_, rows),
       base::Bind(&AutocompleteActionPredictor::CreateCaches, AsWeakPtr(),
                  base::Owned(rows)));
 }
 
 void AutocompleteActionPredictor::DeleteAllRows() {
-  if (!initialized_)
-    return;
+  DCHECK(initialized_);
 
   db_cache_.clear();
   db_id_cache_.clear();
 
   if (table_.get()) {
     content::BrowserThread::PostTask(
         content::BrowserThread::DB, FROM_HERE,
         base::Bind(&AutocompleteActionPredictorTable::DeleteAllRows, table_));
   }
 
   UMA_HISTOGRAM_ENUMERATION("AutocompleteActionPredictor.DatabaseAction",
                             DATABASE_ACTION_DELETE_ALL, DATABASE_ACTION_COUNT);
 }
 
 void AutocompleteActionPredictor::DeleteRowsWithURLs(
     const history::URLRows& rows) {
-  if (!initialized_)
-    return;
+  DCHECK(initialized_);
 
   std::vector<AutocompleteActionPredictorTable::Row::Id> id_list;
 
   for (DBCacheMap::iterator it = db_cache_.begin(); it != db_cache_.end();) {
     if (std::find_if(rows.begin(), rows.end(),
                      history::URLRow::URLRowHasURL(it->first.url)) !=
         rows.end()) {
       const DBIdCacheMap::iterator id_it = db_id_cache_.find(it->first);
       DCHECK(id_it != db_id_cache_.end());
       id_list.push_back(id_it->second);
@@ skipping 67 matching lines @@
     const DBCacheKey key = { it->user_text, it->url };
     const DBCacheValue value = { it->number_of_hits, it->number_of_misses };
     db_cache_[key] = value;
     db_id_cache_[key] = it->id;
   }
 
   // If the history service is ready, delete any old or invalid entries.
   history::HistoryService* history_service =
       HistoryServiceFactory::GetForProfile(profile_,
                                            ServiceAccessType::EXPLICIT_ACCESS);
-  if (!TryDeleteOldEntries(history_service)) {
-    // Wait for the notification that the history service is ready and the URL
-    // DB is loaded.
-    if (history_service)
-      history_service_observer_.Add(history_service);
-  }
+  TryDeleteOldEntries(history_service);
+  if (history_service)

[pasko, 2016/12/15 15:29:48]

nit: extra check for the pointer in TryDeleteOldEntries is fine, but every
reader of these lines would have to go there and check whether it is done, which
is an expensive seek :)

this would look safer and more natural:
if (history_service) {
  TryDeleteOldEntries(history_service);
  history_service_observer_.Add(history_service);
}

+    history_service_observer_.Add(history_service);
 }
 
-bool AutocompleteActionPredictor::TryDeleteOldEntries(
+void AutocompleteActionPredictor::TryDeleteOldEntries(
     history::HistoryService* service) {
   CHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   DCHECK(!profile_->IsOffTheRecord());
   DCHECK(!initialized_);
 
   if (!service)
-    return false;
+    return;
 
   history::URLDatabase* url_db = service->InMemoryDatabase();
   if (!url_db)
-    return false;
+    return;
 
   DeleteOldEntries(url_db);
-  return true;
 }
 
 void AutocompleteActionPredictor::DeleteOldEntries(
     history::URLDatabase* url_db) {
   CHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   DCHECK(!profile_->IsOffTheRecord());
   DCHECK(!initialized_);
   DCHECK(table_.get());
 
   std::vector<AutocompleteActionPredictorTable::Row::Id> ids_to_delete;
@@ skipping 84 matching lines @@
 void AutocompleteActionPredictor::Shutdown() {
   history_service_observer_.RemoveAll();
 }
 
 void AutocompleteActionPredictor::OnURLsDeleted(
     history::HistoryService* history_service,
     bool all_history,
     bool expired,
     const history::URLRows& deleted_rows,
     const std::set<GURL>& favicon_urls) {
-  if (!initialized_)
-    return;
+  DCHECK(initialized_);
 
   if (all_history)
     DeleteAllRows();
   else
     DeleteRowsWithURLs(deleted_rows);
 }
 
 void AutocompleteActionPredictor::OnHistoryServiceLoaded(
     history::HistoryService* history_service) {
-  TryDeleteOldEntries(history_service);
-  history_service_observer_.Remove(history_service);
+  if (!initialized_)
+    TryDeleteOldEntries(history_service);
 }
 
 AutocompleteActionPredictor::TransitionalMatch::TransitionalMatch() {
 }
 
 AutocompleteActionPredictor::TransitionalMatch::TransitionalMatch(
     const TransitionalMatch& other) = default;
 
 AutocompleteActionPredictor::TransitionalMatch::~TransitionalMatch() {
 }
 
 }  // namespace predictors