Tabs API is usable without tabs permission.

chrome/browser/extensions/browser_extension_window_controller.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_EXTENSIONS_BROWSER_EXTENSION_WINDOW_CONTROLLER_H_
 #define CHROME_BROWSER_EXTENSIONS_BROWSER_EXTENSION_WINDOW_CONTROLLER_H_
 
 #include "chrome/browser/extensions/window_controller.h"
 
 class Browser;
 
+namespace extensions {
+class Extension;
+}
+
 class BrowserExtensionWindowController : public extensions::WindowController {
  public:
   explicit BrowserExtensionWindowController(Browser* browser);
   virtual ~BrowserExtensionWindowController();
 
   // extensions::WindowController implementation.
   virtual int GetWindowId() const OVERRIDE;
   virtual std::string GetWindowTypeText() const OVERRIDE;
   virtual base::DictionaryValue* CreateWindowValue() const OVERRIDE;
-  virtual base::DictionaryValue* CreateWindowValueWithTabs() const OVERRIDE;
+  virtual base::DictionaryValue* CreateWindowValueWithTabs(
+      const extensions::Extension* extension) const OVERRIDE;
   virtual bool CanClose(Reason* reason) const OVERRIDE;
   virtual void SetFullscreenMode(bool is_fullscreen,
                                  const GURL& extension_url) const OVERRIDE;
   virtual Browser* GetBrowser() const OVERRIDE;
   virtual bool IsVisibleToExtension(
       const extensions::Extension* extension) const OVERRIDE;
 
  private:
   Browser* browser_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserExtensionWindowController);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_BROWSER_EXTENSION_WINDOW_CONTROLLER_H_