Merge "Return NonNull and other imports" into stage-aosp-master

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;