Add Process.shell and Process.runShell.

tests/standalone/io/process_echo_util.dart

Index: tests/standalone/io/process_echo_util.dart
diff --git a/editor/tools/plugins/com.google.dart.tools.debug.core_test/data/scripts/test.dart b/tests/standalone/io/process_echo_util.dart
similarity index 79%
copy from editor/tools/plugins/com.google.dart.tools.debug.core_test/data/scripts/test.dart
copy to tests/standalone/io/process_echo_util.dart
index e67e24b968af7775f7d780650dfb1819df5c754f..1cc501d49771fc04b23d8660e6dc8d33b74e2356 100644
--- a/editor/tools/plugins/com.google.dart.tools.debug.core_test/data/scripts/test.dart
+++ b/tests/standalone/io/process_echo_util.dart
@@ -2,8 +2,8 @@
 // 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.
 
+import "dart:io";
+
 void main() {
-  print("1");
-  print("2");
-  print("3");
+  new Options().arguments.forEach(print);
 }