Cope with a race condition in NetworkActionPredictor and NetworkActionPredictorDB initialization.

chrome/browser/autocomplete/network_action_predictor_database.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/autocomplete/network_action_predictor_database.h"
 
 #include "base/bind.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
@@ skipping 71 matching lines @@
 
 NetworkActionPredictorDatabase::NetworkActionPredictorDatabase(Profile* profile)
     : db_path_(profile->GetPath().Append(kNetworkActionPredictorDatabaseName)) {
 }
 
 NetworkActionPredictorDatabase::~NetworkActionPredictorDatabase() {
 }
 
 void NetworkActionPredictorDatabase::Initialize() {
   CHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::DB));
-  CHECK(!canceled_.IsSet());
+
+  if (canceled_.IsSet())
+    return;
+
   db_.set_exclusive_locking();
   if (!db_.Open(db_path_)) {
     canceled_.Set();
     return;
   }
 
   if (!db_.DoesTableExist(kNetworkActionPredictorTableName))
     CreateTable();
 
   LogDatabaseStats(db_path_, &db_);
@@ skipping 149 matching lines @@
   bool success = db_.Execute(base::StringPrintf(
       "CREATE TABLE %s ( "
       "id TEXT PRIMARY KEY, "
       "user_text TEXT, "
       "url TEXT, "
       "number_of_hits INTEGER, "
       "number_of_misses INTEGER)", kNetworkActionPredictorTableName).c_str());
   DCHECK(success) << "Failed to create " << kNetworkActionPredictorTableName
                   << " table.";
 }