[VCN11] Make requestBackgroundNetwork requires handler

Test: atest FrameworksNetTests android.net.cts.ConnectivityManagerTest
Bug: 175662146
Change-Id: Iac9487e8de8bfdd87fc7a0153b228ae2a7ba4e19
diff --git a/framework/src/android/net/ConnectivityManager.java b/framework/src/android/net/ConnectivityManager.java
index 3d1da91..adf22da 100644
--- a/framework/src/android/net/ConnectivityManager.java
+++ b/framework/src/android/net/ConnectivityManager.java
@@ -4992,10 +4992,10 @@
             NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK
     })
     public void requestBackgroundNetwork(@NonNull NetworkRequest request,
-            @Nullable Handler handler, @NonNull NetworkCallback networkCallback) {
+            @NonNull Handler handler, @NonNull NetworkCallback networkCallback) {
         final NetworkCapabilities nc = request.networkCapabilities;
         sendRequestForNetwork(nc, networkCallback, 0, BACKGROUND_REQUEST,
-                TYPE_NONE, handler == null ? getDefaultHandler() : new CallbackHandler(handler));
+                TYPE_NONE, new CallbackHandler(handler));
     }
 
     /**