Add embedded_dart_io source_set for Sky

runtime/bin/embedded_dart_io.cc

Index: runtime/bin/embedded_dart_io.cc
diff --git a/runtime/bin/embedded_dart_io.cc b/runtime/bin/embedded_dart_io.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1b3f40b951d67ef4acc9e8fce6c084255261fc4b
--- /dev/null
+++ b/runtime/bin/embedded_dart_io.cc
@@ -0,0 +1,20 @@
+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// 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.
+
+#include "bin/embedded_dart_io.h"
+
+#include "bin/eventhandler.h"
+#include "bin/thread.h"
+
+namespace dart {
+namespace bin {
+
+void BootstrapDartIo() {
+  // Bootstrap 'dart:io' event handler.
+  Thread::InitOnce();
+  EventHandler::Start();
+}
+
+}  // namespace bin
+}  // namespace dart