update shadowdom polyfill to latest

pkg/shadow_dom/tool/build.sh

+#!/bin/bash
+# Copyright (c) 2013, 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.
+
+# Usage: call directly in the commandline as test/run.sh ensuring that you have
+# both 'dart' and 'content_shell' in your path. Filter tests by passing a
+# pattern as an argument to this script.
+
+# bail on error
+set -e
+
+DIR=$( cd $( dirname "${BASH_SOURCE[0]}" ) && pwd )
+# Note: dartanalyzer and some tests needs to be run from the root directory
+pushd $DIR > /dev/null
+
+SHADOWDOM_REMOTE=https://github.com/dart-lang/ShadowDOM.git
+SHADOWDOM_DIR=../../../third_party/polymer/ShadowDOM
+
+echo "*** Syncing $SHADOWDOM_DIR from $SHADOWDOM_REMOTE"
+if [ -d "$SHADOWDOM_DIR" ]; then
+  pushd $SHADOWDOM_DIR > /dev/null
+  git pull
+  popd
+else
+  git clone --branch shadowdom_patches $SHADOWDOM_REMOTE $SHADOWDOM_DIR
+fi
+
+echo '*** Installing NPM prerequisites'
+npm install
+
+echo '*** Running grunt'
+grunt