options: Fix async font fetching crash

chrome/browser/ui/webui/options/font_settings_handler.h

Index: chrome/browser/ui/webui/options/font_settings_handler.h
diff --git a/chrome/browser/ui/webui/options/font_settings_handler.h b/chrome/browser/ui/webui/options/font_settings_handler.h
index 98da3f3bedeb3de21b0fb202445e342f8ae9b935..171d731b47ff0776e11ef5876e4b65466c100ee4 100644
--- a/chrome/browser/ui/webui/options/font_settings_handler.h
+++ b/chrome/browser/ui/webui/options/font_settings_handler.h
@@ -5,7 +5,9 @@
 #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"
@@ -80,6 +82,8 @@ class FontSettingsHandler : public OptionsPageUIHandler,
                  extensions::ExtensionRegistryObserver>
       extension_registry_observer_;
 
+  base::WeakPtrFactory<FontSettingsHandler> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(FontSettingsHandler);
 };