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

content/browser/download/save_package.cc

Index: content/browser/download/save_package.cc
diff --git a/content/browser/download/save_package.cc b/content/browser/download/save_package.cc
index 82b4153d9e4cc68de1532869463e143596ab243a..d65c77a93c6745b29bb6869d029c3af16787b1ce 100644
--- a/content/browser/download/save_package.cc
+++ b/content/browser/download/save_package.cc
@@ -1145,6 +1145,8 @@ const FilePath::CharType* SavePackage::ExtensionForMimeType(
 }
 
 void SavePackage::GetSaveInfo() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
   // Can't use tab_contents_ in the file thread, so get the data that we need
   // before calling to it.
   FilePath website_save_dir, download_save_dir;
@@ -1166,17 +1168,15 @@ void SavePackage::CreateDirectoryOnFileThread(
     const FilePath& download_save_dir,
     const std::string& mime_type,
     const std::string& accept_langs) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+
+  FilePath default_downloads_dir =
+      download_util::GetDefaultDownloadDirectoryFromPathService();
   FilePath save_dir;
-  // If the default html/websites save folder doesn't exist...
-  if (!file_util::DirectoryExists(website_save_dir)) {
-    // If the default download dir doesn't exist, create it.
-    if (!file_util::DirectoryExists(download_save_dir))
-      file_util::CreateDirectory(download_save_dir);
-    save_dir = download_save_dir;
-  } else {
-    // If it does exist, use the default save dir param.
-    save_dir = website_save_dir;
-  }
+  // Ignores the returned value since the select file dialog should be
+  // displayed in any case.
+  download_util::ChooseSavableDirectory(
+      website_save_dir, download_save_dir, default_downloads_dir, &save_dir);
 
   bool can_save_as_complete = CanSaveAsComplete(mime_type);
   FilePath suggested_filename = GetSuggestedNameForSaveAs(
@@ -1206,6 +1206,8 @@ void SavePackage::CreateDirectoryOnFileThread(
 
 void SavePackage::ContinueGetSaveInfo(const FilePath& suggested_path,
                                       bool can_save_as_complete) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
   // The TabContents which owns this SavePackage may have disappeared during
   // the UI->FILE->UI thread hop of
   // GetSaveInfo->CreateDirectoryOnFileThread->ContinueGetSaveInfo.
@@ -1219,6 +1221,8 @@ void SavePackage::ContinueGetSaveInfo(const FilePath& suggested_path,
 // Called after the save file dialog box returns.
 void SavePackage::OnPathPicked(const FilePath& final_name,
                                SavePackageType type) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
   // Ensure the filename is safe.
   saved_main_file_path_ = final_name;
   // TODO(asanka): This call may block on IO and shouldn't be made