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

chrome/browser/renderer_host/save_file_resource_handler.cc

Index: chrome/browser/renderer_host/save_file_resource_handler.cc
diff --git a/chrome/browser/renderer_host/save_file_resource_handler.cc b/chrome/browser/renderer_host/save_file_resource_handler.cc
index 6f374b558c6eff91765b6e289c7ed63627558c25..67a682e384266f738500f0fe9051bb052a69e791 100644
--- a/chrome/browser/renderer_host/save_file_resource_handler.cc
+++ b/chrome/browser/renderer_host/save_file_resource_handler.cc
@@ -12,15 +12,18 @@
 #include "net/base/io_buffer.h"
 #include "net/url_request/url_request_status.h"
 
-SaveFileResourceHandler::SaveFileResourceHandler(int render_process_host_id,
-                                                 int render_view_id,
-                                                 const GURL& url,
-                                                 SaveFileManager* manager)
+SaveFileResourceHandler::SaveFileResourceHandler(
+    int render_process_host_id,
+    int render_view_id,
+    const GURL& url,
+    const FilePath& default_download_dir,
+    SaveFileManager* manager)
     : save_id_(-1),
       render_process_id_(render_process_host_id),
       render_view_id_(render_view_id),
       url_(url),
       content_length_(0),
+      default_download_dir_(default_download_dir),
       save_manager_(manager) {
 }
 
@@ -52,6 +55,8 @@ bool SaveFileResourceHandler::OnResponseStarted(int request_id,
   info->request_id = request_id;
   info->content_disposition = content_disposition_;
   info->save_source = SaveFileCreateInfo::SAVE_FILE_FROM_NET;
+  info->default_download_dir = default_download_dir_;
+
   BrowserThread::PostTask(
       BrowserThread::FILE, FROM_HERE,
       NewRunnableMethod(save_manager_,