Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/ui/zoom/zoom_controller.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/zoom/zoom_controller.h"
 
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser_finder.h"
 #include "chrome/browser/ui/tab_contents/tab_contents.h"
@@ skipping 47 matching lines @@
     const content::LoadCommittedDetails& details,
     const content::FrameNavigateParams& params) {
   // If the main frame's content has changed, the new page may have a different
   // zoom level from the old one.
   UpdateState(std::string());
 }
 
 void ZoomController::Observe(int type,
                              const content::NotificationSource& source,
                              const content::NotificationDetails& details) {
-  switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      std::string* pref_name = content::Details<std::string>(details).ptr();
-      DCHECK(pref_name && *pref_name == prefs::kDefaultZoomLevel);
-      UpdateState(std::string());
-      break;
-    }
-    case content::NOTIFICATION_ZOOM_LEVEL_CHANGED:
-      UpdateState(*content::Details<std::string>(details).ptr());
-      break;
-    default:
-      NOTREACHED();
-  }
+  DCHECK_EQ(content::NOTIFICATION_ZOOM_LEVEL_CHANGED, type);
+  UpdateState(*content::Details<std::string>(details).ptr());
+}
+
+void ZoomController::OnPreferenceChanged(PrefServiceBase* service,
+                                         const std::string& pref_name) {
+  DCHECK(pref_name == prefs::kDefaultZoomLevel);
+  UpdateState(std::string());
 }
 
 void ZoomController::UpdateState(const std::string& host) {
   if (host.empty())
     return;
 
   // Use the active navigation entry's URL instead of the WebContents' so
   // virtual URLs work (e.g. chrome://settings). http://crbug.com/153950
   content::NavigationEntry* active_entry =
       web_contents()->GetController().GetActiveEntry();
   if (!active_entry ||
       host != net::GetHostOrSpecFromURL(active_entry->GetURL())) {
     return;
   }
 
   bool dummy;
   zoom_percent_ = web_contents()->GetZoomPercent(&dummy, &dummy);
 
   if (observer_)
     observer_->OnZoomChanged(web_contents(), !host.empty());
 }