Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/chromeos/drive/drive_file_system.cc

Index: chrome/browser/chromeos/drive/drive_file_system.cc
diff --git a/chrome/browser/chromeos/drive/drive_file_system.cc b/chrome/browser/chromeos/drive/drive_file_system.cc
index 52c4832120d251c0c86a5291a44e7efb0b33c3df..9b87d6c5d0f40b724560a1154d39ee911ec768d6 100644
--- a/chrome/browser/chromeos/drive/drive_file_system.cc
+++ b/chrome/browser/chromeos/drive/drive_file_system.cc
@@ -2184,21 +2184,14 @@ DriveFileSystemMetadata DriveFileSystem::GetMetadata() const {
   return metadata;
 }
 
-void DriveFileSystem::Observe(int type,
-                              const content::NotificationSource& source,
-                              const content::NotificationDetails& details) {
+void DriveFileSystem::OnPreferenceChanged(PrefServiceBase* service,
+                                          const std::string& pref_name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DCHECK(pref_name == prefs::kDisableDriveHostedFiles);

[Mattias Nissler (ping if slow), 2012/10/30 13:37:07]

same comment regarding if() {} else NOTREACHED();

 
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    PrefService* pref_service = profile_->GetPrefs();
-    std::string* pref_name = content::Details<std::string>(details).ptr();
-    if (*pref_name == prefs::kDisableDriveHostedFiles) {
-      SetHideHostedDocuments(
-          pref_service->GetBoolean(prefs::kDisableDriveHostedFiles));
-    }
-  } else {
-    NOTREACHED();
-  }
+  PrefService* pref_service = profile_->GetPrefs();
+  SetHideHostedDocuments(
+      pref_service->GetBoolean(prefs::kDisableDriveHostedFiles));
 }
 
 void DriveFileSystem::SetHideHostedDocuments(bool hide) {