title: com.google.firebase.messaging.zza: can't find referenced class android.graphics.drawable.AdaptiveIconDrawable
body: <p>I'm trying to implement Firebase Cloud Messaging (FCM) in my application.
  I added following dependency in Build.gradle and tried to build a release build variant. </p>
  
  <blockquote>
    <p>compile 'com.google.firebase:firebase-messaging:15.0.0'</p>
  </blockquote>
  
  <p><strong>Build.gradle</strong></p>
  
  <pre><code>dependencies {
     compile 'com.google.firebase:firebase-core:15.0.0'
     compile 'com.google.firebase:firebase-messaging:15.0.0'
  }
  apply plugin: 'com.google.gms.google-services'
  </code></pre>
  
  <p>Once I tried to build a 'debug' variant it worked fine and Firebase messaging works without any errors. But when I try to build 'release' built varient it outputs following error.</p>
  
  <blockquote>
    <p>Warning:com.google.firebase.messaging.zza: can't find referenced class
    android.graphics.drawable.AdaptiveIconDrawable</p>
  </blockquote>
  
  <p>Can anyone help me with this. Really appreciate your comments. Thanks</p>