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

chrome/browser/ui/browser_dialogs.h

Index: chrome/browser/ui/browser_dialogs.h
diff --git a/chrome/browser/ui/browser_dialogs.h b/chrome/browser/ui/browser_dialogs.h
index 6207ab0a1d6fcbfc79063a5ed919f53e708bf4e0..6445c77b3dd11f902422c8aa1779355bbe0c2668 100644
--- a/chrome/browser/ui/browser_dialogs.h
+++ b/chrome/browser/ui/browser_dialogs.h
@@ -25,6 +25,7 @@ class Browser;
 class GURL;
 class LoginHandler;
 class Profile;
+struct WebApplicationInfo;
 
 namespace content {
 class BrowserContext;
@@ -102,6 +103,21 @@ void ShowCreateChromeAppShortcutsDialog(
     const extensions::Extension* app,
     const base::Callback<void(bool /* created */)>& close_callback);
 
+// Callback type used with the ShowBookmarkAppDialog() method. The boolean
+// parameter is true when the user accepts the dialog. The WebApplicationInfo
+// parameter contains the WebApplicationInfo as edited by the user.
+using ShowBookmarkAppDialogCallback =
+    base::OnceCallback<void(bool, const WebApplicationInfo&)>;
+
+// Shows the Bookmark App bubble.
+// See Extension::InitFromValueFlags::FROM_BOOKMARK for a description of
+// bookmark apps.
+//
+// |web_app_info| is the WebApplicationInfo being converted into an app.
+void ShowBookmarkAppDialog(gfx::NativeWindow parent_window,
+                           const WebApplicationInfo& web_app_info,
+                           ShowBookmarkAppDialogCallback callback);
+
 // Shows a color chooser that reports to the given WebContents.
 content::ColorChooser* ShowColorChooser(content::WebContents* web_contents,
                                         SkColor initial_color);