Add sidebar views implementation using ExtensionSystem SidebarManager

chrome/browser/ui/extensions/extension_action_platform_delegate.h

Index: chrome/browser/ui/extensions/extension_action_platform_delegate.h
diff --git a/chrome/browser/ui/extensions/extension_action_platform_delegate.h b/chrome/browser/ui/extensions/extension_action_platform_delegate.h
index d15405ccbed4091d631cc298cc2925ac84147abc..dd64fe9079898c63c4af0868a0943404a4e5d50b 100644
--- a/chrome/browser/ui/extensions/extension_action_platform_delegate.h
+++ b/chrome/browser/ui/extensions/extension_action_platform_delegate.h
@@ -39,6 +39,11 @@ class ExtensionActionPlatformDelegate {
 
   // Closes the overflow menu, if it was open.
   virtual void CloseOverflowMenu() = 0;
+
+  // Shows a sidebar with a given |sidebar_contents|.
+  virtual void ShowSidebar(content::WebContents* sidebar_contents) = 0;
+  // Hides a sidebar if there are active one.
+  virtual void HideSidebar() = 0;
 };
 
 #endif  // CHROME_BROWSER_UI_EXTENSIONS_EXTENSION_ACTION_PLATFORM_DELEGATE_H_