[NS A24] Add an object to represent changes in assignment

        }

    }

    // An accumulator class to gather the list of changes that result from a rematch.

    // TODO : enrich to represent an entire set of changes to apply.

    private static class NetworkReassignment {

        static class NetworkBgStatePair {

            @NonNull final NetworkAgentInfo mNetwork;

            final boolean mOldBackground;

            NetworkBgStatePair(@NonNull final NetworkAgentInfo network,

                    final boolean oldBackground) {

                mNetwork = network;

                mOldBackground = oldBackground;

            }

        }

        @NonNull private final Set<NetworkBgStatePair> mRematchedNetworks = new ArraySet<>();

        void addRematchedNetwork(@NonNull final NetworkBgStatePair network) {

            mRematchedNetworks.add(network);

        }

    }

    private ArrayMap<NetworkRequestInfo, NetworkAgentInfo> computeRequestReassignmentForNetwork(

            @NonNull final NetworkAgentInfo newNetwork) {

        final int score = newNetwork.getCurrentScore();

    //   needed. A network is needed if it is the best network for

    //   one or more NetworkRequests, or if it is a VPN.

    //

    // - Tears down newNetwork if it just became validated

    //   but turns out to be unneeded.

    // - Writes into the passed reassignment object all changes that should be done for

    //   rematching this network with all requests, to be applied later.

    //

    // NOTE: This function only adds NetworkRequests that "newNetwork" could satisfy,

    // it does not remove NetworkRequests that other Networks could better satisfy.

    // This function should be used when possible instead of {@code rematchAllNetworksAndRequests}

    // as it performs better by a factor of the number of Networks.

    //

    // TODO : stop writing to the passed reassignment. This is temporarily more useful, but

    // it's unidiomatic Java and it's hard to read.

    //

    // @param changes a currently-building list of changes to write to

    // @param newNetwork is the network to be matched against NetworkRequests.

    // @param now the time the rematch starts, as returned by SystemClock.elapsedRealtime();

    private void rematchNetworkAndRequests(NetworkAgentInfo newNetwork, long now) {

    private void rematchNetworkAndRequests(@NonNull final NetworkReassignment changes,

            @NonNull final NetworkAgentInfo newNetwork, final long now) {

        ensureRunningOnConnectivityServiceThread();

        if (!newNetwork.everConnected) return;

        boolean isNewDefault = false;

        NetworkAgentInfo oldDefaultNetwork = null;

        final boolean wasBackgroundNetwork = newNetwork.isBackgroundNetwork();

        changes.addRematchedNetwork(new NetworkReassignment.NetworkBgStatePair(newNetwork,

                wasBackgroundNetwork));

        final int score = newNetwork.getCurrentScore();

        if (VDBG || DDBG) log("rematching " + newNetwork.name());

        // scoring network and then a higher scoring network, which could produce multiple

        // callbacks.

        Arrays.sort(nais);

        final NetworkReassignment changes = new NetworkReassignment();

        for (final NetworkAgentInfo nai : nais) {

            rematchNetworkAndRequests(nai, now);

            rematchNetworkAndRequests(changes, nai, now);

        }

        final NetworkAgentInfo newDefaultNetwork = getDefaultNetwork();