[android] - annotate onMapReady with @NonNull

platform/android/MapboxGLAndroidSDKTestApp/src/androidTest/java/com/mapbox/mapboxsdk/testapp/utils/OnMapReadyIdlingResource.java

@@ -3,6 +3,7 @@ package com.mapbox.mapboxsdk.testapp.utils;
 import android.app.Activity;
 import android.os.Handler;
 import android.os.Looper;
+import android.support.annotation.NonNull;
 import android.support.annotation.WorkerThread;
 import android.support.test.espresso.IdlingResource;
 
@@ -49,7 +50,7 @@ public class OnMapReadyIdlingResource implements IdlingResource, OnMapReadyCallb
   }
 
   @Override
-  public void onMapReady(MapboxMap mapboxMap) {
+  public void onMapReady(@NonNull MapboxMap mapboxMap) {
     Assert.assertNotNull("MapboxMap should not be null", mapboxMap);
     this.mapboxMap = mapboxMap;
     if (resourceCallback != null) {