Remove the last usages of PrefObserver outside of Prefs.

chrome/browser/net/net_error_tab_helper.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/net_error_tab_helper.h"
 
 #include "base/bind.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/io_thread.h"
 #include "chrome/browser/net/dns_probe_service.h"
@@ skipping 63 matching lines @@
   // Unit tests don't pass a WebContents, so the tab helper has no way to get
   // to the preference.  pref_initialized_ will remain false, so ProbesAllowed
   // will return false without checking the pref.
   if (!contents)
     return;
 
   BrowserContext* browser_context = contents->GetBrowserContext();
   Profile* profile = Profile::FromBrowserContext(browser_context);
   resolve_errors_with_web_service_.Init(
       prefs::kAlternateErrorPagesEnabled,
-      profile->GetPrefs(),
-      NULL /* no observer */);
+      profile->GetPrefs());
   pref_initialized_ = true;
 }
 
 NetErrorTabHelper::~NetErrorTabHelper() {
 }
 
 void NetErrorTabHelper::DidFailProvisionalLoad(
     int64 frame_id,
     bool is_main_frame,
     const GURL& validated_url,
@@ skipping 42 matching lines @@
   // TODO(ttuttle): Disable on mobile?
   return (pref_initialized_ && *resolve_errors_with_web_service_)
          && enabled_for_testing_;
 }
 
 void NetErrorTabHelper::set_enabled_for_testing(bool enabled_for_testing) {
   enabled_for_testing_ = enabled_for_testing;
 }
 
 }  // namespace chrome_browser_net