Fix browser launch on the login screen.

ui/web_dialogs/web_dialog_delegate.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 UI_WEB_DIALOGS_WEB_DIALOG_DELEGATE_H_
 #define UI_WEB_DIALOGS_WEB_DIALOG_DELEGATE_H_
 
 #include <string>
 #include <vector>
 
 #include "base/strings/string16.h"
+#include "content/public/browser/web_contents_delegate.h"
 #include "ui/base/ui_base_types.h"
 #include "ui/base/window_open_disposition.h"
 #include "ui/web_dialogs/web_dialogs_export.h"
 
 class GURL;
 
 namespace content {
 class RenderViewHost;
 class WebContents;
 class WebUI;
@@ skipping 99 matching lines @@
   // WebContent where the operation originated. |disposition| controls how the
   // new tab should be opened. |initial_pos| is the position of the window if a
   // new window is created. |user_gesture| is true if the operation was started
   // by a user gesture. Return false to use the default handler.
   virtual bool HandleAddNewContents(content::WebContents* source,
                                     content::WebContents* new_contents,
                                     WindowOpenDisposition disposition,
                                     const gfx::Rect& initial_pos,
                                     bool user_gesture);
 
+  // A callback to control whether a WebContents will be created. Returns
+  // false to disallow the creation. Return true to use the default handler.
+  virtual bool HandleShouldCreateWebContents();
+
   // Stores the dialog bounds.
   virtual void StoreDialogSize(const gfx::Size& dialog_size) {}
 
   virtual ~WebDialogDelegate() {}
 };
 
 }  // namespace ui
 
 #endif  // UI_WEB_DIALOGS_WEB_DIALOG_DELEGATE_H_