Remove old InputStream and OutputStream classes from dart:io.

sdk/lib/io/stdio.dart

Index: sdk/lib/io/stdio.dart
diff --git a/sdk/lib/io/stdio.dart b/sdk/lib/io/stdio.dart
index d460edde2f642edf366142ceae7e568420cd9de1..eb7119c95836348e88cf9e51aa68536d88e9b92c 100644
--- a/sdk/lib/io/stdio.dart
+++ b/sdk/lib/io/stdio.dart
@@ -75,7 +75,7 @@ StdioType stdioType(object) {
 
 
 class _StdIOUtils {
-  external static OutputStream _getStdioOutputStream(int fd);
-  external static InputStream _getStdioInputStream();
+  external static IOSink _getStdioOutputStream(int fd);
+  external static Stream<List<int>> _getStdioInputStream();
   external static int _socketType(nativeSocket);
 }