Clean up threading model of external extension providers

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 {
-    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));
-    }
-  }
-  set_prefs(dictionary.release());
-}