[translate] Fix shutdown race for translate ranker model loader.

components/translate/core/browser/translate_download_manager.cc

 // Copyright 2014 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 "components/translate/core/browser/translate_download_manager.h"
 
 #include "base/logging.h"
 #include "base/memory/singleton.h"
 #include "components/prefs/pref_service.h"
 #include "components/translate/core/browser/translate_pref_names.h"
 #include "components/translate/core/common/translate_switches.h"
 
 namespace translate {
 
 // static
 TranslateDownloadManager* TranslateDownloadManager::GetInstance() {
   return base::Singleton<TranslateDownloadManager>::get();
 }
 
 TranslateDownloadManager::TranslateDownloadManager()
     : language_list_(new TranslateLanguageList),
       script_(new TranslateScript) {}
 
 TranslateDownloadManager::~TranslateDownloadManager() {}
 
 void TranslateDownloadManager::Shutdown() {
+  DCHECK(sequence_checker_.CalledOnValidSequence());
   language_list_.reset();
   script_.reset();
   request_context_ = NULL;
 }
 
 // static
 void TranslateDownloadManager::RequestLanguageList(PrefService* prefs) {
   // We don't want to do this when translate is disabled.
   DCHECK(prefs != NULL);
   if (!prefs->GetBoolean(prefs::kEnableTranslate))
@@ skipping 55 matching lines @@
 
 void TranslateDownloadManager::ClearTranslateScriptForTesting() {
   if (script_.get() == NULL) {
     NOTREACHED();
     return;
   }
   script_->Clear();
 }
 
 void TranslateDownloadManager::ResetForTesting() {
+  DCHECK(sequence_checker_.CalledOnValidSequence());
   language_list_.reset(new TranslateLanguageList);
   script_.reset(new TranslateScript);
 }
 
 void TranslateDownloadManager::SetTranslateScriptExpirationDelay(int delay_ms) {
+  DCHECK(sequence_checker_.CalledOnValidSequence());
   if (script_.get() == NULL) {
     NOTREACHED();
     return;
   }
   script_->set_expiration_delay(delay_ms);
 }
 
 }  // namespace translate