I'm encountering a very weird issue, only in GNU/Linux.

Consider the following gist that shows an open dialog and presents the resulting filename in the screen: https://gist.github.com/jviotti/b8358165f1694228fbc31e400dbadab6, which you can run by `npm install && npm start`.

Now create a file with a `.img.gz` extension, like `foo.img.gz`. Using the `touch` command is enough.

Try to select it using the gist application. The `.img.gz` extension is replaced by `.zip` (or whatever is the first item of the extensions filter) for some strange reason.

The issue only seems reproducible with files containing multiple extensions, and when a dialog filter is present.
- Electron version: 1.2.5
- Operating system: GNU/Linux (Ubuntu 14.04 and Arch Linux)

atom/browser/ui/file_dialog_gtk.cc
#include "atom/browser/ui/file_dialog.h"
#include "atom/browser/native_window_views.h"
#include "base/callback.h"
#include "base/files/file_util.h"
#include "base/strings/string_util.h"
#include "chrome/browser/ui/libgtk2ui/gtk2_signal.h"
#include "chrome/browser/ui/libgtk2ui/gtk2_util.h"
#include "ui/views/widget/desktop_aura/x11_desktop_handler.h"
namespace file_dialog {
namespace {
gboolean FileFilterCaseInsensitive(const GtkFileFilterInfo* file_info,
                                   std::string* file_extension) {
  
  if (*file_extension == ".*")
    return true;
  return base::EndsWith(
    file_info->filename,
    *file_extension, base::CompareCase::INSENSITIVE_ASCII);
}
void OnFileFilterDataDestroyed(std::string* file_extension) {
  delete file_extension;
}
class FileChooserDialog {