* 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
save_callback_ = callback;
    RunAsynchronous();
  }
  void RunOpenAsynchronous(const OpenDialogCallback& callback) {
    open_callback_ = callback;
    RunAsynchronous();
  }
  base::FilePath GetFileName() const {
    gchar* filename = gtk_file_chooser_get_filename(GTK_FILE_CHOOSER(dialog_));
    const base::FilePath path(filename);
    g_free(filename);
    return path;
  }
  std::vector<base::FilePath> GetFileNames() const {
    std::vector<base::FilePath> paths;
    auto* filenames = gtk_file_chooser_get_filenames(GTK_FILE_CHOOSER(dialog_));
    for (auto* iter = filenames; iter != NULL; iter = iter->next) {
      auto* filename = static_cast<char*>(iter->data);
      paths.emplace_back(filename);
      g_free(filename);
    }
    g_slist_free(filenames);
    return paths;
  }
  CHROMEG_CALLBACK_1(FileChooserDialog,
                     void,
                     OnFileDialogResponse,
                     GtkWidget*,
                     int);
  GtkWidget* dialog() const { return dialog_; }