[VCN10] Add new API to listen for highest score network

Test: atest ConnectivityServiceTest#testRegisterBestMatchingNetworkCallback
Bug: 175662146
Change-Id: Ifa411c7b53da789c74fff7e1a95f9c9ebf5bd05c
diff --git a/framework/src/android/net/ConnectivityManager.java b/framework/src/android/net/ConnectivityManager.java
index 45ed317..3d1da91 100644
--- a/framework/src/android/net/ConnectivityManager.java
+++ b/framework/src/android/net/ConnectivityManager.java
@@ -20,6 +20,7 @@
 import static android.net.NetworkRequest.Type.BACKGROUND_REQUEST;
 import static android.net.NetworkRequest.Type.LISTEN;
 import static android.net.NetworkRequest.Type.REQUEST;
+import static android.net.NetworkRequest.Type.TRACK_BEST;
 import static android.net.NetworkRequest.Type.TRACK_DEFAULT;
 import static android.net.NetworkRequest.Type.TRACK_SYSTEM_DEFAULT;
 import static android.net.QosCallback.QosCallbackRegistrationException;
@@ -4190,6 +4191,18 @@
     }
 
     /**
+     * @hide
+     */
+    // TODO: Make it public api.
+    @SuppressLint("ExecutorRegistration")
+    public void registerBestMatchingNetworkCallback(@NonNull NetworkRequest request,
+            @NonNull NetworkCallback networkCallback, @NonNull Handler handler) {
+        final NetworkCapabilities nc = request.networkCapabilities;
+        final CallbackHandler cbHandler = new CallbackHandler(handler);
+        sendRequestForNetwork(nc, networkCallback, 0, TRACK_BEST, TYPE_NONE, cbHandler);
+    }
+
+    /**
      * Requests bandwidth update for a given {@link Network} and returns whether the update request
      * is accepted by ConnectivityService. Once accepted, ConnectivityService will poll underlying
      * network connection for updated bandwidth information. The caller will be notified via
diff --git a/framework/src/android/net/NetworkRequest.java b/framework/src/android/net/NetworkRequest.java
index b4a651c..59b539a 100644
--- a/framework/src/android/net/NetworkRequest.java
+++ b/framework/src/android/net/NetworkRequest.java
@@ -113,6 +113,10 @@
      *       for the network (if any) that satisfies the default Internet
      *       request.
      *
+     *     - TRACK_BEST, which causes the framework to send callbacks about
+     *       the single, highest scoring current network (if any) that matches
+     *       the specified NetworkCapabilities.
+     *
      *     - BACKGROUND_REQUEST, like REQUEST but does not cause any networks
      *       to retain the NET_CAPABILITY_FOREGROUND capability. A network with
      *       no foreground requests is in the background. A network that has
@@ -135,6 +139,7 @@
         REQUEST,
         BACKGROUND_REQUEST,
         TRACK_SYSTEM_DEFAULT,
+        TRACK_BEST,
     };
 
     /**