delete observe from the repo

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 53 matching lines @@
 
 analysis_server/test/search/element_references_test: Pass, Slow
 analysis_server/test/services/index/store/codec_test: Pass, Slow
 analysis_server/test/edit/assists_test: Pass, Slow
 
 # Analysis server integration tests don't make sense to run under
 # dart2js, since the code under test always runs in the Dart vm as a
 # subprocess.
 analysis_server/test/integration: Skip
 
-observe/test/unique_message_test: Skip # Intended only as a vm test.
 code_transformers/test/unique_message_test: Skip # Intended only as a vm test.
 
 [ $compiler == dart2js && $checked ]
 crypto/test/base64_test: Slow, Pass
 
 
 [ $compiler == dart2js && $runtime == drt ]
 third_party/angular_tests/browser_test/core_dom/shadow_root_options: Fail # Issue 19329
 
 [ $compiler == dart2js && $csp && $runtime == drt ]
@@ skipping 38 matching lines @@
 source_maps/test/vlq_test: RuntimeError # A VLQ test checks for large numbers that
                                 # overflow in JS (numbers slightly larger than
                                 # 32 bits where we do bitwise operations).
 
 [ $runtime == opera && $compiler == dart2js ]
 intl/test/find_default_locale_browser_test: Fail
 intl/test/date_time_format_http_request_test: Skip # Timeout.
 
 [ $ie ]
 intl/test/date_time_format_http_request_test: Fail # Issue 8983
-observe/test/list_path_observer_test: RuntimeError, Pass # Issue 20849
 
 [ $runtime == ie10 ]
 analyzer/test/generated/java_core_test: Pass, Timeout # Issue 19747
 typed_data/test/typed_buffers_test/none: Fail # Issue   17607 (I put this here explicitly, since this is not the same as on ie9)
 
 [ $runtime == safarimobilesim ]
 # Unexplained errors only occuring on Safari 6.1 and earlier.
 typed_data/test/typed_buffers_test: RuntimeError
 
 
@@ skipping 143 matching lines @@
 third_party/angular_tests/browser_test/core/scope: Skip # Requires checked mode.
 third_party/angular_tests/browser_test/core/zone: Skip # Requires checked mode.
 third_party/angular_tests/browser_test/directive/ng_repeat: Skip # Issue 17152
 third_party/angular_tests/browser_test/change_detection/dirty_checking_change_detector: Skip # Issue 17152
 
 [ $use_repository_packages ]
 analyzer/test/*: PubGetError
 
 [ $runtime == drt ]
 http/test/html/client_test: Skip # Issue 18566