Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/ui/webui/ntp/ntp_resource_cache.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/ui/webui/ntp/ntp_resource_cache.h"
 
 #include <string>
 #include <vector>
 
 #include "base/command_line.h"
@@ skipping 200 matching lines @@
 void NTPResourceCache::Observe(int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
   // Invalidate the cache.
   if (chrome::NOTIFICATION_BROWSER_THEME_CHANGED == type ||
       chrome::NOTIFICATION_PROMO_RESOURCE_STATE_CHANGED == type) {
     new_tab_incognito_html_ = NULL;
     new_tab_html_ = NULL;
     new_tab_incognito_css_ = NULL;
     new_tab_css_ = NULL;
-  } else if (chrome::NOTIFICATION_PREF_CHANGED == type) {
-    // A change occurred to one of the preferences we care about, so flush the
-    // cache.
-    new_tab_incognito_html_ = NULL;
-    new_tab_html_ = NULL;
-    new_tab_css_ = NULL;
   } else if (chrome::NOTIFICATION_NTP_BACKGROUND_THEME_Y_POS_CHANGED == type) {
     css_background_y_pos_ = *(content::Details<int>(details).ptr());
     if (new_tab_css_.get())
       UpdateNewTabCSSBackgroundPosition();
   } else {
     NOTREACHED();
   }
 }
 
+void NTPResourceCache::OnPreferenceChanged(PrefServiceBase* service,
+                                           const std::string& pref_name) {
+  // A change occurred to one of the preferences we care about, so flush the
+  // cache.
+  new_tab_incognito_html_ = NULL;
+  new_tab_html_ = NULL;
+  new_tab_css_ = NULL;
+}
+
 void NTPResourceCache::CreateNewTabIncognitoHTML() {
   DictionaryValue localized_strings;
   localized_strings.SetString("title",
       l10n_util::GetStringUTF16(IDS_NEW_TAB_TITLE));
   int new_tab_message_ids = IDS_NEW_TAB_OTR_MESSAGE;
   int new_tab_html_idr = IDR_INCOGNITO_TAB_HTML;
   const char* new_tab_link = kLearnMoreIncognitoUrl;
   // TODO(altimofeev): consider implementation without 'if def' usage.
 #if defined(OS_CHROMEOS)
   if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kGuestSession)) {
@@ skipping 384 matching lines @@
       kCSSBackgroundPositionDelimiter, background_pos_start);
   DCHECK(background_pos_end != std::string::npos);
   std::string new_background_pos = GetNewTabBackgroundCSS(
       ThemeServiceFactory::GetForProfile(profile_), false);
   new_css_string.replace(background_pos_start,
                          background_pos_end - background_pos_start,
                          new_background_pos);
 
   new_tab_css_ = base::RefCountedString::TakeString(&new_css_string);
 }