Make isEmpty a getter.

tests/standalone/standalone.status

 # Copyright (c) 2012, 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.
 
 out_of_memory_test: Skip # Issue 2345
 
 package/invalid_uri_test: Fail, OK # Fails intentionally
 
 [ $runtime == vm ]
 # The following tests require files in the tools-directory to be modified.
 # However the tools directory uses its own version of dart-binary. We reenable
 # these tests when we update the dart-binary.
 status_expression_test: Fail, OK
 io/status_file_parser_test: Fail, OK
+io/test_runner_exit_code_test: Fail, OK
 
 [ $compiler == dart2js || ($compiler == none && $runtime == drt) ]
 # The following tests require files in the tools-directory to be modified.
 # However the tools directory uses its own version of dart-binary. We reenable
 # these tests when we update the dart-binary.
 status_expression_test: Fail, OK
 
 [ $runtime == vm && $checked ]
 # These tests have type errors on purpose.
 io/process_invalid_arguments_test: Fail, OK
@@ skipping 57 matching lines @@
 [ $compiler == dart2js && $browser ]
 *: Skip
 
 [ $compiler == dart2js && $checked ]
 io/http_read_test: Skip # Timeout TODO(ngeoffray): investigate
 io/list_input_stream_test: Skip # Timeout TODO(ngeoffray): investigate
 
 [ $compiler == dart2dart ]
 # Skip until we stabilize language tests.
 *: Skip