Add support to specify the source address for socket connect

sdk/lib/_internal/compiler/js_lib/io_patch.dart

Index: sdk/lib/_internal/compiler/js_lib/io_patch.dart
diff --git a/sdk/lib/_internal/compiler/js_lib/io_patch.dart b/sdk/lib/_internal/compiler/js_lib/io_patch.dart
index ee38707f4f57d542ee17c4d178ef0dbe414e081a..d2b3e0ff8a83a36362491ce884018dea485fa4de 100644
--- a/sdk/lib/_internal/compiler/js_lib/io_patch.dart
+++ b/sdk/lib/_internal/compiler/js_lib/io_patch.dart
@@ -378,7 +378,7 @@ class ServerSocket {
 @patch
 class RawSocket {
   @patch
-  static Future<RawSocket> connect(host, int port) {
+  static Future<RawSocket> connect(host, int port, {sourceAddress}) {
     throw new UnsupportedError("RawSocket constructor");
   }
 }
@@ -386,7 +386,7 @@ class RawSocket {
 @patch
 class Socket {
   @patch
-  static Future<Socket> connect(host, int port) {
+  static Future<Socket> connect(host, int port, {sourceAddress}) {
     throw new UnsupportedError("Socket constructor");
   }
 }