title: Proguard obfuscation issues after adding new Google Sign In to Android application
body: <p>In the new Google Play Services library (8.3.0) there is a new way to perform sign-in. This method involves adding the following dependencies:</p>
  
  <p>build.gradle (app level):
  <code>classpath 'com.google.gms:google-services:1.4.0-beta3'</code></p>
  
  <p>And on app level:</p>
  
  <pre><code>compile 'com.google.android.gms:play-services-auth:8.3.0'
  
  `apply plugin: 'com.google.gms.google-services'`
  </code></pre>
  
  <p>When creating a release app version with <code>minifyEnabled</code> set to <code>false</code>, the app is being released and works fine. However, when creating a release version with 
  <code>minifyEnabled</code> set to <code>true</code> the app crashes on startup with the following exception:</p>
  
  <pre><code>java.lang.RuntimeException: Unable to get provider com.google.android.gms.measurement.AppMeasurementContentProvider: java.lang.ClassNotFoundException: Didn't find class "com.google.android.gms.measurement.AppMeasurementContentProvider" on path: DexPathList[[zip file "/data/app/com.xxx.xxx-1/base.apk"],nativeLibraryDirectories=[/data/app/com.xxx.xxx-1/lib/arm, /vendor/lib, /system/lib]]
  11-08 12:47:13.497 3672-3672/? E/AndroidRuntime:     at android.app.ActivityThread.installProvider(ActivityThread.java:5156)
  11-08 12:47:13.497 3672-3672/? E/AndroidRuntime:     at android.app.ActivityThread.installContentProviders(ActivityThread.java:4748)
  11-08 12:47:13.497 3672-3672/? E/AndroidRuntime:     at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4688)
  11-08 12:47:13.497 3672-3672/? E/AndroidRuntime:     at android.app.ActivityThread.-wrap1(ActivityThread.java)
  11-08 12:47:13.497 3672-3672/? E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1405)
  11-08 12:47:13.497 3672-3672/? E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:102)
  11-08 12:47:13.497 3672-3672/? E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:148)
  11-08 12:47:13.497 3672-3672/? E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5417)
  11-08 12:47:13.497 3672-3672/? E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Native Method)
  11-08 12:47:13.497 3672-3672/? E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
  11-08 12:47:13.497 3672-3672/? E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
  11-08 12:47:13.497 3672-3672/? E/AndroidRuntime:  Caused by: java.lang.ClassNotFoundException: Didn't find class "com.google.android.gms.measurement.AppMeasurementContentProvider" on path: DexPathList[[zip file "/data/app/xxx.xxx...
  </code></pre>
  
  <p>I have tried to add these settings to the proguard project config but it doesn't help (same exception keeps appearing):</p>
  
  <pre><code>-optimizationpasses 5
  -keepattributes SourceFile,LineNumberTable,Exceptions, Signature, InnerClasses,*Annotation*
  -keep class com.google.android.gms.** { *; }
  -dontwarn com.google.android.gms.**
  </code></pre>