Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm

 // 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.
 
 #import "chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/message_loop.h"
 #include "base/stl_util.h"
@@ skipping 575 matching lines @@
     }
 
     case chrome::NOTIFICATION_EXTENSION_LOCATION_BAR_UPDATED: {
       // Only update if the updated action box was for the active tab contents.
       WebContents* target_tab = content::Details<WebContents>(details).ptr();
       if (target_tab == GetTabContents()->web_contents())
         UpdatePageActions();
       break;
     }
 
-    case chrome::NOTIFICATION_PREF_CHANGED:
-      UpdateStarDecorationVisibility();
-      OnChanged();
-      break;
-
     default:
       NOTREACHED() << "Unexpected notification";
       break;
   }
 }
 
+void LocationBarViewMac::OnPreferenceChanged(PrefServiceBase* service,
+                                             const std::string& pref_name) {
+  UpdateStarDecorationVisibility();
+  OnChanged();
+}
+
 void LocationBarViewMac::PostNotification(NSString* notification) {
   [[NSNotificationCenter defaultCenter] postNotificationName:notification
                                         object:[NSValue valueWithPointer:this]];
 }
 
 bool LocationBarViewMac::RefreshContentSettingsDecorations() {
   const bool input_in_progress = toolbar_model_->GetInputInProgress();
   WebContents* web_contents =
       input_in_progress ? NULL : chrome::GetActiveWebContents(browser_);
   bool icons_updated = false;
@@ skipping 164 matching lines @@
     visible = false;
   star_decoration_->SetVisible(visible);
 }
 
 void LocationBarViewMac::UpdatePlusDecorationVisibility() {
   if (extensions::FeatureSwitch::action_box()->IsEnabled()) {
     // If the action box is enabled, hide it when input is in progress.
     plus_decoration_->SetVisible(!toolbar_model_->GetInputInProgress());
   }
 }