title: ProGuard: can't find referenced class com.google.android.gms.R
body: <p>After some updates in Android SDK manager I try make signed apk and get this: </p>
  
  <pre><code>ProGuard: [] Warning: com.google.android.gms.auth.GoogleAuthUtil: 
    can't find referenced class com.google.android.gms.R
  ProGuard: [] Warning: com.google.android.gms.auth.GoogleAuthUtil: 
    can't find referenced class com.google.android.gms.R$string
  ...
  etc.
  </code></pre>
  
  <p>If set <code>-dontwarn com.google.android.gms.**</code> compiling is OK. But after run I get error many reports like this (from many devices):</p>
  
  <pre><code>Caused by: android.view.InflateException: Binary XML file line #32: 
    Error inflating class com.google.android.gms.common.SignInButton
  </code></pre>
  
  <p>On my devices all ok. Before update I have not ProGuard warnings and all work perfectly. How it fix?</p>