* 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
confirm_text, GTK_RESPONSE_ACCEPT, NULL);
    if (parent_) {
      parent_->SetEnabled(false);
      libgtkui::SetGtkTransientForAura(dialog_, parent_->GetNativeWindow());
      gtk_window_set_modal(GTK_WINDOW(dialog_), TRUE);
    }
    if (action == GTK_FILE_CHOOSER_ACTION_SAVE)
      gtk_file_chooser_set_do_overwrite_confirmation(GTK_FILE_CHOOSER(dialog_),
                                                     TRUE);
    if (action != GTK_FILE_CHOOSER_ACTION_OPEN)
      gtk_file_chooser_set_create_folders(GTK_FILE_CHOOSER(dialog_), TRUE);
    if (!settings.default_path.empty()) {
      if (base::DirectoryExists(settings.default_path)) {
        gtk_file_chooser_set_current_folder(
            GTK_FILE_CHOOSER(dialog_), settings.default_path.value().c_str());
      } else {
        if (settings.default_path.IsAbsolute()) {
          gtk_file_chooser_set_current_folder(
              GTK_FILE_CHOOSER(dialog_),
              settings.default_path.DirName().value().c_str());
        }
        gtk_file_chooser_set_current_name(
            GTK_FILE_CHOOSER(dialog_),
            settings.default_path.BaseName().value().c_str());
      }
    }
    if (!settings.filters.empty())
      AddFilters(settings.filters);
  }
  ~FileChooserDialog() {