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

chrome/browser/download/download_util.h

Index: chrome/browser/download/download_util.h
diff --git a/chrome/browser/download/download_util.h b/chrome/browser/download/download_util.h
index e7726a9d28ac646f4aa640c022bee14a006139b2..0b726816c2ce8d1e8c65fef0a7f73fe9b6c421c3 100644
--- a/chrome/browser/download/download_util.h
+++ b/chrome/browser/download/download_util.h
@@ -51,8 +51,27 @@ 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.