Updating Shadow DOM and including some fixes to enable it to work with CustomElements.

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 47 matching lines @@
 [ $runtime == safari ]
 fixnum/test/int_64_test: Pass, Fail # Bug in JSC.
 crypto/test/hmac_sha1_test: Pass, Fail # Issue 11407.
 crypto/test/sha1_test: Fail # Issue 11407.
 stack_trace/test/trace_test: Fail # http://dartbug.com/12380
 crypto/test/sha256_test: Pass, Fail # Issue 12502
 crypto/test/hmac_sha256_test: Pass, Fail # Issue 12502
 polymer/test/events_test: Fail # Issue 12865, 13197
 polymer/test/event_path_test: Fail # Issue 12865, 13197
 
-[ $runtime == ff ]
-polymer/test/event_path_test: Fail # Issue 12865, 13197
-
 [ $runtime == ie9 || $runtime == ie10 ]
 polymer/test/events_test: Fail, Timeout # Issue 12865, 13197, 13260
 polymer/test/event_path_test: Fail, Timeout # Issue 12865, 13197, 13260
 
 [ $system == windows && ($runtime == chrome || $runtime == ff) ]
 polymer/test/events_test: Pass, Timeout # Issue 13260
 polymer/test/event_path_test: Pass, Timeout # Issue 13260
 
 # Skip browser-specific tests on VM
 [ $runtime == vm ]
@@ skipping 143 matching lines @@
 
 [ $runtime == safari || $runtime == chrome || $runtime == ie9 || $runtime == ff || $runtime == dartium || $runtime == drt ]
 docgen/test/single_library_test: Skip # Uses dart:io
 
 [ $browser || $runtime == vm ]
 unittest/test/missing_tick_test: Fail, OK # This test should fail, not time out.
 
 # Issue http://dartbug.com/12930
 [ $runtime == vm ]
 intl/test/message_extraction/message_extraction_test: Pass, Fail # Issue 12930