[Mac] Add cocoa implementation for sidebar extension action support

chrome/browser/ui/cocoa/extensions/extension_action_platform_delegate_cocoa.h

 // Copyright 2014 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_COCOA_EXTENSIONS_EXTENSION_ACTION_PLATFORM_DELEGATE_COCOA_H_
 #define CHROME_BROWSER_UI_COCOA_EXTENSIONS_EXTENSION_ACTION_PLATFORM_DELEGATE_COCOA_H_
 
 #import <Foundation/Foundation.h>
 
 #include "chrome/browser/ui/extensions/extension_action_platform_delegate.h"
@@ skipping 13 matching lines @@
 
  private:
   // ExtensionActionPlatformDelegate:
   void RegisterCommand() override;
   void OnDelegateSet() override;
   void ShowPopup(
       scoped_ptr<extensions::ExtensionViewHost> host,
       bool grant_tab_permissions,
       ExtensionActionViewController::PopupShowAction show_action) override;
   void CloseOverflowMenu() override;
+  void ShowSidebar(content::WebContents* sidebar_contents) override;
+  void HideSidebar() override;
 
   // content::NotificationObserver:
   void Observe(int type,
                const content::NotificationSource& source,
                const content::NotificationDetails& details) override;
 
   // Returns the point at which the popup should be shown.
   NSPoint GetPopupPoint() const;
 
   // The main controller for this extension action.
   ExtensionActionViewController* controller_;
 
   content::NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionActionPlatformDelegateCocoa);
 };
 
 #endif  // CHROME_BROWSER_UI_COCOA_EXTENSIONS_EXTENSION_ACTION_PLATFORM_DELEGATE_COCOA_H_