When the download folder does not exist, change the download folder to a user's "Downloads"

chrome/browser/ui/webui/options/advanced_options_handler.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_WEBUI_OPTIONS_ADVANCED_OPTIONS_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_OPTIONS_ADVANCED_OPTIONS_HANDLER_H_
 #pragma once
 
 #include "chrome/browser/prefs/pref_member.h"
 #include "chrome/browser/prefs/pref_set_observer.h"
 #include "chrome/browser/printing/cloud_print/cloud_print_setup_handler.h"
 #include "chrome/browser/ui/shell_dialogs.h"
 #include "chrome/browser/ui/webui/options/options_ui.h"
 
 class CloudPrintSetupHandler;
 
 // Chrome advanced options page UI handler.
 class AdvancedOptionsHandler
     : public OptionsPageUIHandler,
       public SelectFileDialog::Listener,
       public CloudPrintSetupHandlerDelegate {
  public:
+
+  class DownloadPathChecker
+      : public base::RefCountedThreadSafe<DownloadPathChecker> {
+   public:
+    explicit DownloadPathChecker(AdvancedOptionsHandler* handler);
+
+    // Check if the download folder still exists. If the download folder
+    // does not exist, the download folder is changed to the user's
+    // "Downloads" folder. This check runs in the background and may finish
+    // asynchronously after this method returns.
+    void CheckIfDownloadPathExists(const FilePath& path);
+
+   private:
+    friend class base::RefCountedThreadSafe<DownloadPathChecker>;
+    ~DownloadPathChecker();
+
+    // Called on the FILE thread to check the existence of the download folder.
+    // If it does not exist, this method tells the user's "Downloads"
+    // to OnDownloadPathChanged().
+    void CheckIfDownloadPathExistsOnFileThread(const FilePath& path);
+
+    // Called on the UI thread when the FILE thread finds that the download
+    // folder does not exist. This method changes the download folder to
+    // the user's "Downloads" folder and notifies this preference change
+    // to observers.
+    void OnDownloadPathChanged(const FilePath path);
+
+    // The handler we will report back to.
+    AdvancedOptionsHandler* handler_;
+  };
+
   AdvancedOptionsHandler();
   virtual ~AdvancedOptionsHandler();
 
   // OptionsPageUIHandler implementation.
   virtual void GetLocalizedValues(DictionaryValue* localized_strings);
   virtual void Initialize();
 
   // WebUIMessageHandler implementation.
   virtual WebUIMessageHandler* Attach(WebUI* web_ui);
   virtual void RegisterMessages();
@@ skipping 92 matching lines @@
 #endif
 
   // Setup the checked state for the metrics reporting checkbox.
   void SetupMetricsReportingCheckbox();
 
   // Setup the visibility for the metrics reporting setting.
   void SetupMetricsReportingSettingVisibility();
 
   void SetupFontSizeLabel();
 
-  // Setup the download path based on user preferences.
+  // Setup the download folder based on user preferences.
   void SetupDownloadLocationPath();
 
   // Setup the pref whether to prompt for download location every time.
   void SetupPromptForDownload();
 
   // Setup the enabled state of the reset button.
   void SetupAutoOpenFileTypesDisabledAttribute();
 
   // Setup the proxy settings section UI.
   void SetupProxySettingsSection();
 
   // Setup the checked state for SSL related checkboxes.
   void SetupSSLConfigSettings();
 
+  scoped_refptr<DownloadPathChecker> download_path_checker_;
+
   scoped_refptr<SelectFileDialog> select_folder_dialog_;
 
 #if !defined(OS_CHROMEOS)
   BooleanPrefMember enable_metrics_recording_;
   StringPrefMember cloud_print_proxy_email_;
   BooleanPrefMember cloud_print_proxy_enabled_;
   bool cloud_print_proxy_ui_enabled_;
   scoped_ptr<CloudPrintSetupHandler> cloud_print_setup_handler_;
 #endif
 
 #if !defined(OS_MACOSX) && !defined(OS_CHROMEOS)
   BooleanPrefMember background_mode_enabled_;
 #endif
 
   FilePathPrefMember default_download_location_;
   BooleanPrefMember ask_for_save_location_;
   BooleanPrefMember allow_file_selection_dialogs_;
   StringPrefMember auto_open_files_;
   IntegerPrefMember default_font_size_;
   scoped_ptr<PrefSetObserver> proxy_prefs_;
 
   DISALLOW_COPY_AND_ASSIGN(AdvancedOptionsHandler);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_OPTIONS_ADVANCED_OPTIONS_HANDLER_H_