Remove the last usages of PrefObserver outside of Prefs.

chrome/browser/net/chrome_http_user_agent_settings.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/net/chrome_http_user_agent_settings.h"
 
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/common/pref_names.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/common/content_client.h"
 #include "net/http/http_util.h"
 
 ChromeHttpUserAgentSettings::ChromeHttpUserAgentSettings(PrefService* prefs) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
-  pref_accept_language_.Init(prefs::kAcceptLanguages, prefs, NULL);
-  pref_accept_charset_.Init(prefs::kDefaultCharset, prefs, NULL);
+  pref_accept_language_.Init(prefs::kAcceptLanguages, prefs);
+  pref_accept_charset_.Init(prefs::kDefaultCharset, prefs);
   last_pref_accept_language_ = *pref_accept_language_;
   last_http_accept_language_ =
       net::HttpUtil::GenerateAcceptLanguageHeader(last_pref_accept_language_);
   last_pref_accept_charset_ = *pref_accept_charset_;
   last_http_accept_charset_ =
       net::HttpUtil::GenerateAcceptCharsetHeader(last_pref_accept_charset_);
   pref_accept_language_.MoveToThread(
       content::BrowserThread::GetMessageLoopProxyForThread(
           content::BrowserThread::IO));
   pref_accept_charset_.MoveToThread(
@@ skipping 31 matching lines @@
     last_pref_accept_charset_ = new_pref_accept_charset;
   }
   return last_http_accept_charset_;
 }
 
 std::string ChromeHttpUserAgentSettings::GetUserAgent(const GURL& url) const {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
   return content::GetUserAgent(url);
 }