Remove the last usages of PrefObserver outside of Prefs.

chrome/browser/download/download_prefs.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/download/download_prefs.h"
 
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 21 matching lines @@
 #include "chrome/browser/chromeos/drive/drive_file_system_util.h"
 #include "chrome/browser/chromeos/drive/drive_system_service.h"
 #endif
 
 using content::BrowserContext;
 using content::BrowserThread;
 using content::DownloadManager;
 
 DownloadPrefs::DownloadPrefs(Profile* profile) : profile_(profile) {
   PrefService* prefs = profile->GetPrefs();
-  prompt_for_download_.Init(prefs::kPromptForDownload, prefs, NULL);
-  download_path_.Init(prefs::kDownloadDefaultDirectory, prefs, NULL);
-  save_file_type_.Init(prefs::kSaveFileType, prefs, NULL);
+  prompt_for_download_.Init(prefs::kPromptForDownload, prefs);
+  download_path_.Init(prefs::kDownloadDefaultDirectory, prefs);
+  save_file_type_.Init(prefs::kSaveFileType, prefs);
 
   // We store any file extension that should be opened automatically at
   // download completion in this pref.
   std::string extensions_to_open =
       prefs->GetString(prefs::kDownloadExtensionsToOpen);
   std::vector<std::string> extensions;
   base::SplitString(extensions_to_open, ':', &extensions);
 
   for (size_t i = 0; i < extensions.size(); ++i) {
 #if defined(OS_POSIX)
@@ skipping 145 matching lines @@
     extensions.erase(extensions.size() - 1);
 
   profile_->GetPrefs()->SetString(prefs::kDownloadExtensionsToOpen, extensions);
 }
 
 bool DownloadPrefs::AutoOpenCompareFunctor::operator()(
     const FilePath::StringType& a,
     const FilePath::StringType& b) const {
   return FilePath::CompareLessIgnoreCase(a, b);
 }