Add DCHECKs to StatefulExternalExtensionProvider

chrome/browser/extensions/external_pref_extension_provider.cc

 // Copyright (c) 2010 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/extensions/external_pref_extension_provider.h"
 
 #include "app/app_paths.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/path_service.h"
+#include "chrome/browser/browser_thread.h"
 #include "chrome/browser/extensions/stateful_external_extension_provider.h"
 #include "chrome/common/json_value_serializer.h"
 
 ExternalPrefExtensionProvider::ExternalPrefExtensionProvider()
   : StatefulExternalExtensionProvider(Extension::EXTERNAL_PREF,
                                       Extension::EXTERNAL_PREF_DOWNLOAD) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   FilePath json_file;
   PathService::Get(app::DIR_EXTERNAL_EXTENSIONS, &json_file);
   json_file = json_file.Append(FILE_PATH_LITERAL("external_extensions.json"));
 
   if (file_util::PathExists(json_file)) {
     JSONFileValueSerializer serializer(json_file);
     SetPreferences(&serializer);
   } else {
-    prefs_.reset(new DictionaryValue());
+    set_prefs(new DictionaryValue());
   }
 }
 
 ExternalPrefExtensionProvider::~ExternalPrefExtensionProvider() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 }
 
 void ExternalPrefExtensionProvider::SetPreferencesForTesting(
     const std::string& json_data_for_testing) {
   JSONStringValueSerializer serializer(json_data_for_testing);
   SetPreferences(&serializer);
 }
 
 void ExternalPrefExtensionProvider::SetPreferences(
     ValueSerializer* serializer) {
   std::string error_msg;
   Value* extensions = serializer->Deserialize(NULL, &error_msg);
   scoped_ptr<DictionaryValue> dictionary(new DictionaryValue());
   if (!extensions) {
     LOG(WARNING) << "Unable to deserialize json data: " << error_msg;
   } else {
     if (!extensions->IsType(Value::TYPE_DICTIONARY)) {
       NOTREACHED() << "Invalid json data";
     } else {
       dictionary.reset(static_cast<DictionaryValue*>(extensions));
     }
   }
-  prefs_.reset(dictionary.release());
+  set_prefs(dictionary.release());
 }