Add "not congested" network capability.

Can be used by a network to indicate when it's congested, meaning that
apps should defer network traffic that could be done at a later time.

Test: bit FrameworksNetTests:android.net.,com.android.server.net.,com.android.server.connectivity.VpnTest,com.android.server.ConnectivityServiceTest
Bug: 64133169
Change-Id: Iddc32fb40ba74b4b936ecaf97f29a54b04f540f9
diff --git a/service/java/com/android/server/wifi/WifiStateMachine.java b/service/java/com/android/server/wifi/WifiStateMachine.java
index ff3aea9..2eab721 100644
--- a/service/java/com/android/server/wifi/WifiStateMachine.java
+++ b/service/java/com/android/server/wifi/WifiStateMachine.java
@@ -980,6 +980,7 @@
         mNetworkCapabilitiesFilter.addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
         mNetworkCapabilitiesFilter.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_METERED);
         mNetworkCapabilitiesFilter.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_ROAMING);
+        mNetworkCapabilitiesFilter.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_CONGESTED);
         mNetworkCapabilitiesFilter.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_RESTRICTED);
         mNetworkCapabilitiesFilter.setLinkUpstreamBandwidthKbps(1024 * 1024);
         mNetworkCapabilitiesFilter.setLinkDownstreamBandwidthKbps(1024 * 1024);