Make NetworkCapabilities publicly immutable.

Applying API council comments.

bug: 15142362
Change-Id: Ie0bde68b72656a676d90c0343b9756fe9268d8d6
diff --git a/java/com/android/server/ethernet/EthernetNetworkFactory.java b/java/com/android/server/ethernet/EthernetNetworkFactory.java
index 820e16b..483f983 100644
--- a/java/com/android/server/ethernet/EthernetNetworkFactory.java
+++ b/java/com/android/server/ethernet/EthernetNetworkFactory.java
@@ -391,9 +391,8 @@
     private void initNetworkCapabilities() {
         mNetworkCapabilities = new NetworkCapabilities();
         mNetworkCapabilities.addTransportType(NetworkCapabilities.TRANSPORT_ETHERNET);
-        mNetworkCapabilities.addNetworkCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
-        mNetworkCapabilities.addNetworkCapability(
-                NetworkCapabilities.NET_CAPABILITY_NOT_RESTRICTED);
+        mNetworkCapabilities.addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
+        mNetworkCapabilities.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_RESTRICTED);
         // We have no useful data on bandwidth. Say 100M up and 100M down. :-(
         mNetworkCapabilities.setLinkUpstreamBandwidthKbps(100 * 1000);
         mNetworkCapabilities.setLinkDownstreamBandwidthKbps(100 * 1000);