[Mac] Add cocoa implementation for sidebar extension action support

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

Index: chrome/browser/ui/cocoa/extensions/extension_action_platform_delegate_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/extensions/extension_action_platform_delegate_cocoa.mm b/chrome/browser/ui/cocoa/extensions/extension_action_platform_delegate_cocoa.mm
index 1de9d70c60b504eafc70d9ba8846139f66935a27..bf7c79828656dc52bc4d66079b47d0c9da614d5c 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_action_platform_delegate_cocoa.mm
+++ b/chrome/browser/ui/cocoa/extensions/extension_action_platform_delegate_cocoa.mm
@@ -12,6 +12,7 @@
 #include "chrome/browser/extensions/extension_view_host.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_window.h"
+#import "chrome/browser/ui/cocoa/browser_window_cocoa.h"
 #import "chrome/browser/ui/cocoa/browser_window_controller.h"
 #import "chrome/browser/ui/cocoa/extensions/browser_actions_controller.h"
 #import "chrome/browser/ui/cocoa/extensions/extension_popup_controller.h"
@@ -92,6 +93,19 @@ void ExtensionActionPlatformDelegateCocoa::CloseOverflowMenu() {
     [wrenchMenuController cancel];
 }
 
+void ExtensionActionPlatformDelegateCocoa::ShowSidebar(
+    content::WebContents* sidebar_contents) {
+  BrowserWindowCocoa* window =
+      static_cast<BrowserWindowCocoa*>(controller_->browser()->window());
+  window->ShowSidebar(sidebar_contents);
+}
+
+void ExtensionActionPlatformDelegateCocoa::HideSidebar() {
+  BrowserWindowCocoa* window =
+      static_cast<BrowserWindowCocoa*>(controller_->browser()->window());
+  window->HideSidebar();
+}
+
 NSPoint ExtensionActionPlatformDelegateCocoa::GetPopupPoint() const {
   BrowserWindowController* windowController =
       [BrowserWindowController browserWindowControllerForWindow: