Use BookmarkAppConfirmationView on Mac. Delete the NSAlert Mac uses currently.

chrome/test/base/test_browser_window.h

Index: chrome/test/base/test_browser_window.h
diff --git a/chrome/test/base/test_browser_window.h b/chrome/test/base/test_browser_window.h
index 7701ac79c7068cad0749b2e2d22d17bc7f490a88..1cdd3d819d5336fa048b25252e1e2a55b883de82 100644
--- a/chrome/test/base/test_browser_window.h
+++ b/chrome/test/base/test_browser_window.h
@@ -91,9 +91,6 @@ class TestBrowserWindow : public BrowserWindow {
   bool IsToolbarShowing() const override;
   void ShowUpdateChromeDialog() override {}
   void ShowBookmarkBubble(const GURL& url, bool already_bookmarked) override {}
-  void ShowBookmarkAppBubble(
-      const WebApplicationInfo& web_app_info,
-      const ShowBookmarkAppBubbleCallback& callback) override {}
   autofill::SaveCardBubbleView* ShowSaveCreditCardBubble(
       content::WebContents* contents,
       autofill::SaveCardBubbleController* controller,