fix csslib and watcher warnings

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 292 matching lines @@
 
 [ $compiler == dartanalyzer ]
 # pkg issue 13944; Missing inherited member 'Observable._mirror'
 custom_element/test/analyzer_test: fail
 
 [ $compiler == dart2analyzer ]
 # pkg issue 13944; Missing inherited members: 'ListChangeRecord.addedCount' and 'ListChangeRecord.removedCount'
 custom_element/test/analyzer_test: fail
 
 [ $compiler == dartanalyzer || $compiler == dart2analyzer ]
-csslib/test/big_1_test: StaticWarning
-csslib/test/compiler_test: StaticWarning
-csslib/test/declaration_test: StaticWarning
-csslib/test/error_test: StaticWarning
-csslib/test/extend_test: StaticWarning
-csslib/test/mixin_test: StaticWarning
-csslib/test/nested_test: StaticWarning
-csslib/test/selector_test: StaticWarning
-csslib/test/var_test: StaticWarning
-csslib/test/visitor_test: StaticWarning
 docgen/test/single_library_test: StaticWarning
 http_server/test/http_body_test: StaticWarning
 http_server/test/http_multipart_test: StaticWarning
 http_server/test/virtual_directory_test: StaticWarning
 http_server/test/virtual_host_test: StaticWarning
 http/test/client_test: StaticWarning
 http/test/http_test: StaticWarning
 http/test/mock_client_test: StaticWarning
 http/test/multipart_test: StaticWarning
 http/test/request_test: StaticWarning
 http/test/streamed_request_test: StaticWarning
 intl/test/date_time_format_file_even_test: StaticWarning
 intl/test/date_time_format_file_odd_test: StaticWarning
 intl/test/date_time_format_http_request_test: StaticWarning
 intl/test/date_time_format_local_even_test: StaticWarning
 intl/test/date_time_format_local_odd_test: StaticWarning
-unittest/test/matchers_test: StaticWarning
-unittest/test/mock_test: StaticWarning
-watcher/test/directory_watcher_test: StaticWarning
-watcher/test/no_subscription_test: StaticWarning
-watcher/test/ready_test: StaticWarning
+unittest/test/matchers_test: StaticWarning, OK # testing error creating abstract class
+unittest/test/mock_test: StaticWarning, OK # testing unimplemented members
 
 [ $runtime == vm ]
 # Issue surfaced after removing deprecated async features.
 scheduled_test/test/scheduled_test/nested_task_test: RuntimeError # Issue 14639