Return NonNull and other imports

Change-Id: Ia38b13209b45d8228ac02f06663e4dc12be9de60
diff --git a/core/java/android/net/NetworkUtils.java b/core/java/android/net/NetworkUtils.java
index e6472e9..d0f54b4 100644
--- a/core/java/android/net/NetworkUtils.java
+++ b/core/java/android/net/NetworkUtils.java
@@ -16,10 +16,15 @@
 
 package android.net;
 
+import static android.system.OsConstants.AF_INET;
+import static android.system.OsConstants.AF_INET6;
+
+import android.annotation.NonNull;
 import android.annotation.UnsupportedAppUsage;
 import android.net.shared.Inet4AddressUtils;
 import android.os.Build;
 import android.system.ErrnoException;
+import android.system.Os;
 import android.util.Log;
 import android.util.Pair;