Add link to the Advanced Font Settings extension in Font Settings

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/memory/scoped_ptr.h"
 #include "base/prefs/pref_member.h"
 #include "chrome/browser/ui/webui/options/options_ui.h"
+#include "content/public/browser/notification_observer.h"
 
 namespace base {
 class ListValue;
 }
 
+namespace extensions {
+class Extension;
+}
+
 namespace options {
 
 // Font settings overlay page UI handler.
 class FontSettingsHandler : public OptionsPageUIHandler {
  public:
   FontSettingsHandler();
   virtual ~FontSettingsHandler();
 
   // OptionsPageUIHandler implementation.
   virtual void GetLocalizedValues(DictionaryValue* localized_strings) OVERRIDE;
+  virtual void InitializeHandler() OVERRIDE;
   virtual void InitializePage() OVERRIDE;
 
   // WebUIMessageHandler implementation.
   virtual void RegisterMessages() OVERRIDE;
 
  private:
+  // content::NotificationObserver (from OptionsPageUIHandler) implementation
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+
   void HandleFetchFontsData(const ListValue* args);
 
   void FontsListHasLoaded(scoped_ptr<base::ListValue> list);
 
   void SetUpStandardFontSample();
   void SetUpSerifFontSample();
   void SetUpSansSerifFontSample();
   void SetUpFixedFontSample();
   void SetUpMinimumFontSample();
+
+  const extensions::Extension* GetAdvancedFontSettingsExtension();
+  void NotifyAdvancedFontSettingsAvailability();
+  void OpenAdvancedFontSettingsOptions(const base::ListValue* args);
+
   void OnWebKitDefaultFontSizeChanged();
 
   StringPrefMember standard_font_;
   StringPrefMember serif_font_;
   StringPrefMember sans_serif_font_;
   StringPrefMember fixed_font_;
   StringPrefMember font_encoding_;
   IntegerPrefMember default_font_size_;
   IntegerPrefMember default_fixed_font_size_;
   IntegerPrefMember minimum_font_size_;
 
+  content::NotificationRegistrar registrar_;
+
   DISALLOW_COPY_AND_ASSIGN(FontSettingsHandler);
 };
 
 }  // namespace options
 
 #endif  // CHROME_BROWSER_UI_WEBUI_OPTIONS_FONT_SETTINGS_HANDLER_H_