Reinitialize LocalState's CommandLinePrefStore after about_flags updates the command line.

chrome/browser/prefs/testing_pref_store.h

Index: chrome/browser/prefs/testing_pref_store.h
===================================================================
--- chrome/browser/prefs/testing_pref_store.h	(revision 118876)
+++ chrome/browser/prefs/testing_pref_store.h	(working copy)
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -6,6 +6,8 @@
 #define CHROME_BROWSER_PREFS_TESTING_PREF_STORE_H_
 #pragma once
 
+#include <string>
+
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
@@ -25,6 +27,7 @@
                               const base::Value** result) const OVERRIDE;
   virtual void AddObserver(PrefStore::Observer* observer) OVERRIDE;
   virtual void RemoveObserver(PrefStore::Observer* observer) OVERRIDE;
+  virtual size_t NumberOfObservers() const OVERRIDE;
   virtual bool IsInitializationComplete() const OVERRIDE;
 
   // PersistentPrefStore overrides: