Add builder tag for Safari 6.2 slave. Update status files for Safari 6.2.

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 248 matching lines @@
 [ $runtime == ie10 || $runtime == ie11 ]
 scheduled_test/test/scheduled_test/current_schedule_errors_test: Timeout # Issue 21007
 scheduled_test/test/scheduled_test/nested_task_test: Timeout # Issue 21007
 scheduled_test/test/scheduled_test/out_of_band_task_test: Timeout # Issue 21007
 scheduled_test/test/scheduled_test/signal_error_test: Timeout # Issue 21007
 scheduled_test/test/scheduled_test/task_return_value_test: Timeout # Issue 21007
 scheduled_test/test/scheduled_test/timeout_test: Timeout # Issue 21007
 scheduled_test/test/scheduled_test/wrap_async_test: Timeout # Issue 21007
 scheduled_test/test/scheduled_test/wrap_future_test: Timeout # Issue 21007
 
-[ $runtime == safari || $runtime == safarimobilesim ]
+[ ($runtime == safari && $builder_tag == mac10_7) || $runtime == safarimobilesim ]
 # Unexplained errors only occuring on Safari.
 typed_data/test/typed_buffers_test: RuntimeError
 
 [ $runtime == safari ]
 polymer/test/js_interop_test: Pass, RuntimeError # Issue 20075
 
 [ $runtime == safari || $ie ]
 polymer/test/two_way_bind_test: Pass, RuntimeError # Issue 20075
 
 # Skip browser-specific tests on VM
@@ skipping 208 matching lines @@
 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
 
 [ $system == windows ]
 analysis_server/test/integration/search/get_type_hierarchy_test: Pass, Fail # Issue 20436
+
+[ $runtime == safari && $builder_tag == mac10_8 ]
+polymer/e2e_test/good_import/test/import_test: RuntimeError # Issue 21424
+polymer/test/custom_event_test: RuntimeError # Issue 21425
+polymer/test/instance_attrs_test: RuntimeError # Issue 21425
+polymer/test/property_observe_test: RuntimeError # Issue 21425
+intl/test/date_time_format_http_request_test: RuntimeError # Issue 21428