Add FilePath::FinalExtension() to avoid double extensions (.tar.gz) for file selector

chrome/browser/download/download_file_picker.cc

Index: chrome/browser/download/download_file_picker.cc
diff --git a/chrome/browser/download/download_file_picker.cc b/chrome/browser/download/download_file_picker.cc
index 94dc46297da1b10c5389e3c8abecd054d21d2cd2..a2d2d3e29e06ca730af29579590a1dda8bd9d2bb 100644
--- a/chrome/browser/download/download_file_picker.cc
+++ b/chrome/browser/download/download_file_picker.cc
@@ -69,7 +69,9 @@ DownloadFilePicker::DownloadFilePicker(
   select_file_dialog_ = ui::SelectFileDialog::Create(
       this, new ChromeSelectFilePolicy(web_contents));
   ui::SelectFileDialog::FileTypeInfo file_type_info;
-  base::FilePath::StringType extension = suggested_path_.Extension();
+  // Platform file pickers, notably on Mac and Windows, tend to break
+  // with double extensions like .tar.gz, so only pass in normal ones.
+  base::FilePath::StringType extension = suggested_path_.FinalExtension();
   if (!extension.empty()) {
     extension.erase(extension.begin());  // drop the .
     file_type_info.extensions.resize(1);