Suppress flakiness in pkg/observe/test/list_path_observer_test on IE

pkg/pkg.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.
 
 # Don't run any test-like files that show up in packages directories. It
 # shouldn't be necessary to run "pub install" in these packages, but if you do
 # it shouldn't break the tests.
 */packages/*/*: Skip
 */*/packages/*/*: Skip
 */*/*/packages/*/*: Skip
@@ skipping 218 matching lines @@
 polymer/test/bind_mdv_test: Slow, Pass, RuntimeError # Issue 14412, 13260
 matcher/test/core_matchers_test: RuntimeError # Issue 17762
 polymer_expressions/test/bindings_test: RuntimeError # Issue 19265
 polymer_expressions/test/globals_test: RuntimeError # Issue 19265
 template_binding/test/template_binding_test: Pass, RuntimeError # Issue 19265
 
 [ $ie ]
 polymer/test/noscript_test: RuntimeError, Pass # Issue 13260
 intl/test/date_time_format_http_request_test: Fail # Issue 8983
 polymer_expressions/test/syntax_test: Fail, Timeout, Pass # Issue 19138
+observe/test/list_path_observer_test: RuntimeError, Pass # Issue 20849
 
 [ $runtime == ie10 ]
 typed_data/test/typed_buffers_test/none: Fail # Issue   17607 (I put this here explicitly, since this is not the same as on ie9)
 polymer/e2e_test/*: Pass, RuntimeError # Issue 19265
 polymer_expressions/*: Pass, RuntimeError # Issue 19265
 template_binding/test/template_binding_test: Pass, RuntimeError # Issue 19265
 template_binding/test/custom_element_bindings_test: Pass, RuntimeError # Issue 20714
 polymer/test/event_handlers_test: Pass, Timeout # Issue 19327
 analyzer/test/generated/java_core_test: Pass, Timeout # Issue 19747
 
@@ skipping 233 matching lines @@
 oauth2/test/authorization_code_grant_test: Fail
 oauth2/test/client_test: Fail
 oauth2/test/credentials_test: Fail
 oauth2/test/handle_access_token_response_test: Fail
 
 [ $runtime == drt ]
 http/test/html/client_test: Skip # Issue 18566
 
 [ $system == windows ]
 analysis_server/test/integration/search/get_type_hierarchy_test: Pass, Fail # Issue 20436