title: Web Push notification Payload data is getting null
body: <p>Hi I'm trying to implement web push notification for web i followed the following <a href="https://serviceworke.rs/push-payload_index_doc.html" rel="nofollow">example</a>,except the server part for which i'm using python script to connect to gcm/fcm and generating payload .i'm getting the push event but the event.data coming null .</p>
  
  <pre><code>from datetime import datetime
  from pyfcm import FCMNotification
  pushService = FCMNotification(api_key ='xxx'}
  registrationId=""
  messageTitle = "New update available"
  messageBody ="some message"
  dryRun = False
  extraData = {}
  extraData['title'] = "nknkn"
  </code></pre>
  
  <p>sw.js</p>
  
  <pre><code>self.addEventListener('push',function(e){
  
  console.log('Push Message Recevied',e.data);
  var title = 'Push message';
  e.waitUntil(
      self.registration.showNotification(title, {
          body: 'The Message form data',
          icon: 'icon.jpg',
          tag: 'my-tag'
      }));
  });
  </code></pre>