* 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
public:
  FileChooserDialog(GtkFileChooserAction action, const DialogSettings& settings)
      : parent_(static_cast<atom::NativeWindowViews*>(settings.parent_window)),
        filters_(settings.filters) {
    const char* confirm_text = _("_OK");
    if (!settings.button_label.empty())
      confirm_text = settings.button_label.c_str();
    else if (action == GTK_FILE_CHOOSER_ACTION_SAVE)
      confirm_text = _("_Save");
    else if (action == GTK_FILE_CHOOSER_ACTION_OPEN)
      confirm_text = _("_Open");
    dialog_ = gtk_file_chooser_dialog_new(
        settings.title.c_str(), NULL, action, _("_Cancel"), GTK_RESPONSE_CANCEL,