Add tests for panel app icon functionaility.

chrome/browser/ui/panels/native_panel.h

Index: chrome/browser/ui/panels/native_panel.h
diff --git a/chrome/browser/ui/panels/native_panel.h b/chrome/browser/ui/panels/native_panel.h
index 7a58ee16f66feb3bd5775e1fceacda2fa59b2d8a..bcca384a474a0858cba60334e0f4857a03e73dee 100644
--- a/chrome/browser/ui/panels/native_panel.h
+++ b/chrome/browser/ui/panels/native_panel.h
@@ -26,6 +26,7 @@ class NativePanel {
   friend class Panel;
   friend class PanelBrowserWindow;
   friend class PanelBrowserTest;
+  friend class PanelExtensionBrowserTest;
 
  protected:
   virtual ~NativePanel() {}
@@ -110,6 +111,9 @@ class NativePanelTesting {
   // Verifies, on a deepest possible level, if the native panel is really
   // active, i.e. the titlebar is painted per its active state.
   virtual bool VerifyActiveState(bool is_active) = 0;
+  // Verifies, on a deepest possible level, if the native panel is really
+  // showing a correct app icon (taskbar icon).
+  virtual bool VerifyAppIcon() const = 0;
   virtual void WaitForWindowCreationToComplete() const { }
 
   virtual bool IsWindowSizeKnown() const = 0;