Don't expose raw IBinder APIs.

APIs should not expose raw IBinder objects.

Fix: 184735751
Test: builds, boots
Test: atest CtsNetTestCases:android.net.cts.ConnectivityManagerTest
Test: atest CtsNetTestCases:android.net.cts.DnsResolverTest
Change-Id: Ia0c4170def31123f0b79318fec2cfe02e4fcd3bf

services/core/java/com/android/server/ConnectivityService.java

@@ -616,7 +616,9 @@ public class ConnectivityService extends IConnectivityManager.Stub
     }
 
     private static IDnsResolver getDnsResolver(Context context) {
-        return IDnsResolver.Stub.asInterface(DnsResolverServiceManager.getService(context));
+        final DnsResolverServiceManager dsm = context.getSystemService(
+                DnsResolverServiceManager.class);
+        return IDnsResolver.Stub.asInterface(dsm.getService());
     }
 
     /** Handler thread used for all of the handlers below. */