Tabs API is usable without tabs permission.

chrome/browser/ui/panels/panel.cc

Index: chrome/browser/ui/panels/panel.cc
diff --git a/chrome/browser/ui/panels/panel.cc b/chrome/browser/ui/panels/panel.cc
index ac995394bfeebeb01ec39b4da3c441bad5c0c070..68c9e1cc93bb79262fd0b5cdb5831ba29e706404 100644
--- a/chrome/browser/ui/panels/panel.cc
+++ b/chrome/browser/ui/panels/panel.cc
@@ -37,6 +37,10 @@
 using content::RenderViewHost;
 using content::UserMetricsAction;
 
+namespace extensions {
+class Extension;
+}
+
 namespace panel_internal {
 
 class PanelExtensionWindowController : public extensions::WindowController {
@@ -47,7 +51,8 @@ class PanelExtensionWindowController : public extensions::WindowController {
   // Overridden from extensions::WindowController.
   virtual int GetWindowId() const OVERRIDE;
   virtual std::string GetWindowTypeText() 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;
@@ -79,7 +84,8 @@ std::string PanelExtensionWindowController::GetWindowTypeText() const {
 }
 
 base::DictionaryValue*
-PanelExtensionWindowController::CreateWindowValueWithTabs() const {
+PanelExtensionWindowController::CreateWindowValueWithTabs(
+    const extensions::Extension* extension) const {
   return CreateWindowValue();
 }