Add reverse dns lookup as a method on InternetAddress.

runtime/bin/socket_patch.dart

Index: runtime/bin/socket_patch.dart
diff --git a/runtime/bin/socket_patch.dart b/runtime/bin/socket_patch.dart
index 3caf14806bc3f7f152d4248485e0a1a3ce8479a9..7c3069a7a0c8e7e710eda4abbf059952c453eea2 100644
--- a/runtime/bin/socket_patch.dart
+++ b/runtime/bin/socket_patch.dart
@@ -104,6 +104,8 @@ class _InternetAddress implements InternetAddress {
     }
   }
 
+  Future<InternetAddress> reverse() => _NativeSocket.reverseLookup(this);
+
   _InternetAddress(InternetAddressType this.type,
                    String this.address,
                    String this.host,
@@ -191,6 +193,7 @@ class _NativeSocket extends NativeFieldWrapperClass1 {
   // Native port messages.
   static const HOST_NAME_LOOKUP = 0;
   static const LIST_INTERFACES = 1;
+  static const REVERSE_LOOKUP = 2;
 
   // Socket close state
   bool isClosed = false;
@@ -234,6 +237,18 @@ class _NativeSocket extends NativeFieldWrapperClass1 {
         });
   }
 
+  static Future<InternetAddress> reverseLookup(InternetAddress addr) {
+    ensureSocketService();
+    return socketService.call([REVERSE_LOOKUP, addr._sockaddr_storage])
+        .then((response) {
+          if (isErrorResponse(response)) {
+            throw createError(response, "Failed host name lookup");
+          } else {
+            return addr._cloneWithNewHost(response);
+          }
+        });
+  }
+
   static Future<List<NetworkInterface>> listInterfaces({
       bool includeLoopback: false,
       bool includeLinkLocal: false,