Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/prefs/pref_value_store.h

 // 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.
 
 #ifndef CHROME_BROWSER_PREFS_PREF_VALUE_STORE_H_
 #define CHROME_BROWSER_PREFS_PREF_VALUE_STORE_H_
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/prefs/pref_store.h"
 #include "base/values.h"
-#include "content/public/browser/browser_thread.h"
 
 class PrefModelAssociator;
 class PrefNotifier;
 class PrefStore;
 
 // The PrefValueStore manages various sources of values for Preferences
 // (e.g., configuration policies, extensions, and user settings). It returns
 // the value of a Preference from the source with the highest priority, and
 // allows setting user-defined values for preferences that are not managed.
 //
@@ skipping 219 matching lines @@
   // A mapping of preference names to their registered types.
   PrefTypeMap pref_types_;
 
   // True if not all of the PrefStores were initialized successfully.
   bool initialization_failed_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefValueStore);
 };
 
 #endif  // CHROME_BROWSER_PREFS_PREF_VALUE_STORE_H_