title: Can not resolve symbol "FirebaseMessagingService"
body: <p>I'm tring to integrate Firebase Cloud Messaging in android app but facing problem to extend <code>FirebaseMessagingService</code> in our class.</p>
  
  <p>It displaying <strong>Can not resolve symbol "FirebaseMessagingService"</strong></p>
  
  <p>app.gradle</p>
  
  <pre><code>compile 'com.google.firebase:firebase-core:10.0.1'
  compile 'com.google.firebase:firebase-database:9.8.0'
  </code></pre>
  
  <p>and also add google-service.json file</p>