Add reusePort argument to ServerSocket.

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 ce8ace5476635829bccca0e2998141e430cfa8bf..e8804d5176354954ed8c17dc63de8110f2cffbeb 100644
--- a/sdk/lib/io/socket.dart
+++ b/sdk/lib/io/socket.dart
@@ -194,7 +194,8 @@ abstract class RawServerSocket implements Stream<RawSocket> {
   external static Future<RawServerSocket> bind(address,
                                                int port,
                                                {int backlog: 0,
-                                                bool v6Only: false});
+                                                bool v6Only: false,
+                                                bool reusePort: false});
 
   /**
    * Returns the port used by this socket.
@@ -255,7 +256,8 @@ abstract class ServerSocket implements Stream<Socket> {
   external static Future<ServerSocket> bind(address,
                                             int port,
                                             {int backlog: 0,
-                                             bool v6Only: false});
+                                             bool v6Only: false,
+                                             bool reusePort: false});
 
   /**
    * Returns the port used by this socket.