Migrate dart2js stubs for dart:io

tool/input_sdk/lib/io/eventhandler.dart

Index: tool/input_sdk/lib/io/eventhandler.dart
diff --git a/test/codegen/language/built_in_identifier_prefix_library_as.dart b/tool/input_sdk/lib/io/eventhandler.dart
similarity index 54%
copy from test/codegen/language/built_in_identifier_prefix_library_as.dart
copy to tool/input_sdk/lib/io/eventhandler.dart
index 96ce332ddd63f6edc5193585fe6bd3d4d7094da6..883c2e16b1d24628ddfcdef528fa0538a1dbd5fe 100644
--- a/test/codegen/language/built_in_identifier_prefix_library_as.dart
+++ b/tool/input_sdk/lib/io/eventhandler.dart
@@ -2,13 +2,10 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-library as;
+part of dart.io;
 
-class A {
-}
-
-class B<T> {
-}
-
-class C<T, S> {
+class _EventHandler {
+  external static void _sendData(Object sender,
+                                 SendPort sendPort,
+                                 int data);
 }