options: Fix async font fetching crash

chrome/browser/ui/webui/options/font_settings_handler.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_UI_WEBUI_OPTIONS_FONT_SETTINGS_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_OPTIONS_FONT_SETTINGS_HANDLER_H_
 
+#include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
 #include "base/prefs/pref_member.h"
 #include "base/scoped_observer.h"
 #include "chrome/browser/ui/webui/options/options_ui.h"
 #include "extensions/browser/extension_registry_observer.h"
 
 namespace base {
 class ListValue;
 }
 
 namespace extensions {
@@ skipping 54 matching lines @@
   StringPrefMember fixed_font_;
   StringPrefMember font_encoding_;
   IntegerPrefMember default_font_size_;
   IntegerPrefMember default_fixed_font_size_;
   IntegerPrefMember minimum_font_size_;
 
   ScopedObserver<extensions::ExtensionRegistry,
                  extensions::ExtensionRegistryObserver>
       extension_registry_observer_;
 
+  base::WeakPtrFactory<FontSettingsHandler> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(FontSettingsHandler);
 };
 
 }  // namespace options
 
 #endif  // CHROME_BROWSER_UI_WEBUI_OPTIONS_FONT_SETTINGS_HANDLER_H_