Remove abstract from InternetAddress now that it has a constructor

sdk/lib/io/socket.dart

Index: sdk/lib/io/socket.dart
diff --git a/sdk/lib/io/socket.dart b/sdk/lib/io/socket.dart
index dfb440e9d6e8d0ceae9804613fd46698f61b9a39..2caa90ba864d7934d5054921c30b880fdcf92edb 100644
--- a/sdk/lib/io/socket.dart
+++ b/sdk/lib/io/socket.dart
@@ -46,7 +46,7 @@ class InternetAddressType {
  * endpoint that a socket can connect to or a listening socket can
  * bind to.
  */
-abstract class InternetAddress {
+class InternetAddress {
   /**
    * IP version 4 loopback address. Use this address when listening on
    * or connecting to the loopback adapter using IP version 4 (IPv4).