* Output of `node_modules/.bin/electron --version`: 3.0.10, 4.0.0-beta.7
* Operating System (Platform and Version): Ubuntu 18.04
* Output of `node_modules/.bin/electron --version` on last known working Electron version (if applicable): N/A

**Expected Behavior**
When picking a file to upload, the file picker should show a preview of the file when applicable

**Actual behavior**
It does not show a preview...

Chrome shows a preview of the image (tested with 70 and 69).
![chrome](https://user-images.githubusercontent.com/103586/48838688-01b4f280-ed81-11e8-8b38-16d7cbab1f22.png)

Electron shows no preview
![electron](https://user-images.githubusercontent.com/103586/48838699-08dc0080-ed81-11e8-8611-6a199fba23f8.png)


**To Reproduce**
Nothing special, click on a file upload form element...
```html
<input type="file" />
```
Example here: https://cgi-lib.berkeley.edu/ex/fup.html
atom/browser/ui/file_dialog_gtk.cc
const OpenDialogCallback& callback) {
  GtkFileChooserAction action = GTK_FILE_CHOOSER_ACTION_OPEN;
  if (settings.properties & FILE_DIALOG_OPEN_DIRECTORY)
    action = GTK_FILE_CHOOSER_ACTION_SELECT_FOLDER;
  FileChooserDialog* open_dialog = new FileChooserDialog(action, settings);
  open_dialog->SetupProperties(settings.properties);
  open_dialog->RunOpenAsynchronous(callback);
}
bool ShowSaveDialog(const DialogSettings& settings, base::FilePath* path) {
  FileChooserDialog save_dialog(GTK_FILE_CHOOSER_ACTION_SAVE, settings);
  gtk_widget_show_all(save_dialog.dialog());
  int response = gtk_dialog_run(GTK_DIALOG(save_dialog.dialog()));
  if (response == GTK_RESPONSE_ACCEPT) {
    *path = save_dialog.GetFileName();
    return true;
  } else {
    return false;
  }
}
void ShowSaveDialog(const DialogSettings& settings,
                    const SaveDialogCallback& callback) {
  FileChooserDialog* save_dialog =
      new FileChooserDialog(GTK_FILE_CHOOSER_ACTION_SAVE, settings);
  save_dialog->RunSaveAsynchronous(callback);
}
}