Mark all private functions in dart: libraries as invisible (*sniff*).

tests/standalone/standalone.status

 # Copyright (c) 2013, 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.
 
 # WARNING:
 # Tests using the multitest feature where failure is expected should *also* be
 # listed in tests/lib/analyzer/analyze_tests.status without the "standalone"
 # prefix.
 
 package/invalid_uri_test: Fail, OK # CompileTimeErrors intentionally
 
 issue14236_test: Pass # Do not remove this line. It serves as a marker for Issue 14516 comment #4.
 
 javascript_compatibility_errors_test/none: Fail, OK  # Not possible to exclude or annotate with '/// none:'
 
 [ $runtime == vm ]
 package/package_isolate_test: Fail # Issue 12474
+io/observatory_test: Fail
 
 [ $runtime == vm && $checked ]
 # These tests have type errors on purpose.
 io/process_invalid_arguments_test: Fail, OK
 io/directory_invalid_arguments_test: Fail, OK
 io/file_invalid_arguments_test: Fail, OK
 io/internet_address_invalid_arguments_test: Fail, OK
 io/socket_invalid_arguments_test: Fail, OK
 io/stdout_bad_argument_test: Fail, OK
 # These test have type errors on purpose and take very long to run in
@@ skipping 126 matching lines @@
 
 [ $system == windows ]
 io/skipping_dart2js_compilations_test: Fail # Issue 19551.
 io/stdout_stderr_non_blocking_test: Fail # Issue 22088
 
 [ $system != linux ]
 io/server_socket_reference_issue21383_and_issue21384_test: Skip # Not supported on other platforms so far
 
 [ $arch != ia32 && $arch != x64 && $arch != simarm && $mode == debug ]
 verified_mem_test: Skip  # Not yet implemented.