Don't show FileManagerDialog if another FileManagerDialog is shown in the same tab.

chrome/browser/ui/views/file_manager_dialog.h

 // Copyright (c) 2011 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 CHROME_BROWSER_UI_VIEWS_FILE_MANAGER_DIALOG_H_
 #define CHROME_BROWSER_UI_VIEWS_FILE_MANAGER_DIALOG_H_
 #pragma once
 
 #include <map>
 
@@ skipping 52 matching lines @@
 
   // Closes the dialog and cleans up callbacks and listeners.
   void Close();
 
   // Posts a task to close the dialog.
   void PostTaskToClose();
 
   // Adds this to the list of pending dialogs, used for testing.
   void AddPending(int32 tab_id);
 
+  // Check if the list of pending dialogs contains dialog for |tab_id|.
+  static bool PendingExists(int32 tab_id);
+
   // Returns if the dialog has mutiple file type choices
   virtual bool HasMultipleFileTypeChoicesImpl();
 
   bool hasMultipleFileTypeChoices_;
   void* params_;
 
   // Host for the extension that implements this dialog.
   scoped_refptr<ExtensionDialog> extension_dialog_;
 
   // ID of the tab that spawned this dialog, used to route callbacks.
   int32 tab_id_;
 
   gfx::NativeWindow owner_window_;
 
   DISALLOW_COPY_AND_ASSIGN(FileManagerDialog);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_FILE_MANAGER_DIALOG_H_