[Mac] Add cocoa implementation for sidebar extension action support

chrome/browser/ui/cocoa/browser_window_cocoa.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_COCOA_BROWSER_WINDOW_COCOA_H_
 #define CHROME_BROWSER_UI_COCOA_BROWSER_WINDOW_COCOA_H_
 
 #include "base/mac/scoped_nsobject.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/extensions/extension_keybinding_registry.h"
@@ skipping 161 matching lines @@
   // Overridden from SearchModelObserver:
   void ModelChanged(const SearchModel::State& old_state,
                     const SearchModel::State& new_state) override;
 
   // Adds the given FindBar cocoa controller to this browser window.
   void AddFindBar(FindBarCocoaController* find_bar_cocoa_controller);
 
   // Returns the cocoa-world BrowserWindowController
   BrowserWindowController* cocoa_controller() { return controller_; }
 
+  // Handle Sidebar
+  void ShowSidebar(content::WebContents* sidebar_contents);
+  void HideSidebar();
+
  protected:
   void DestroyBrowser() override;
 
  private:
   NSWindow* window() const;  // Accessor for the (current) |NSWindow|.
+  void UpdateSidebarForContents(content::WebContents* sidebar_contents);
 
   Browser* browser_;  // weak, owned by controller
   BrowserWindowController* controller_;  // weak, owns us
   base::scoped_nsobject<NSString> pending_window_title_;
   ui::WindowShowState initial_show_state_;
   NSInteger attention_request_id_;  // identifier from requestUserAttention
 };
 
 #endif  // CHROME_BROWSER_UI_COCOA_BROWSER_WINDOW_COCOA_H_