title: app.setBadgeCount is not working
body: <pre><code>app.on('ready', function () {
    let self = this;
  
    mainWindow = new BrowserWindow({
      x: mainWindowState.x,
      y: mainWindowState.y,
      width: mainWindowState.width,
      height: mainWindowState.height,
      'node-integration': false,
      preload: __dirname + '/vendor/electron_boilerplate/context_menu.js',
    });
  
    if (process.platform === 'linux') {
      app.getLocale();
      mainWindow.setBadgeCount = 5;
    }
  }
  </code></pre>
  
  <p>Why can't I use electron.app.setBadgeCount() ?</p>