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

chrome/browser/download/download_util.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.
 //
 // Download utilities.
 
 #ifndef CHROME_BROWSER_DOWNLOAD_DOWNLOAD_UTIL_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_UTIL_H_
 #pragma once
 
@@ skipping 33 matching lines @@
 
 namespace gfx {
 class Canvas;
 class Image;
 }
 
 namespace download_util {
 
 // Download temporary file creation --------------------------------------------
 
-// Return the default download directory.
-const FilePath& GetDefaultDownloadDirectory();
+class DefaultDownloadDirectory {
+ public:
+  // Returns the path of the default download folder.
+  // If the path is being overridden, returns the overridden path.
+  static bool Get(FilePath* path);
+
+  // Overrides the path of the default download folder.
+  // WARNING: We can use this method only on testing context (e.g. download
+  // tests) for temporarily switching the default download folder.
+  // WARNING: In order to override the path, we must use
+  // this method instead of using PathService::Override(),
+  // since PathService::Override() can cause many problems:
+  // http://codereview.chromium.org/2805100
+  static void Override(const FilePath& override_path);
+
+  // Invalidate the overriding of the default download folder.
+  static void UnOverride();
+
+ private:
+  static FilePath override_path_;
+};
 
 // Create a temporary file for a download in the user's default download
 // directory and return true if was successful in creating the file.
 bool CreateTemporaryFileForDownload(FilePath* path);
 
 // Return true if the |download_path| is dangerous path.
 bool DownloadPathIsDangerous(const FilePath& download_path);
 
 // Create an extension based on the file name and mime type.
 void GenerateExtension(const FilePath& file_name,
@@ skipping 223 matching lines @@
 // Erases all downloaded files with the specified path and name prefix.
 // Used by download UI tests to clean up the download directory.
 void EraseUniqueDownloadFiles(const FilePath& path_prefix);
 
 // Returns a .crdownload intermediate path for the |suggested_path|.
 FilePath GetCrDownloadPath(const FilePath& suggested_path);
 
 }  // namespace download_util
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_UTIL_H_