Import Polymer 0.8 and several key elements.

third_party/polymer/v0_8/components-chromium/paper-styles/classes/shadow.html

+<!--
+@license
+Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
+This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+Code distributed by Google as part of the polymer project is also
+subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+-->
+
+<style>
+.shadow-transition {
+  transition: box-shadow 0.28s cubic-bezier(0.4, 0, 0.2, 1);
+}
+
+.shadow-elevation-1 {
+  box-shadow: 0 1px 4px 0 rgba(0, 0, 0, 0.37);
+}
+
+.shadow-elevation-2 {
+  box-shadow: 0 2px 2px 0 rgba(0, 0, 0, 0.2),
+              0 6px 10px 0 rgba(0, 0, 0, 0.3);
+}
+
+.shadow-elevation-3 {
+  box-shadow: 0 11px 7px 0 rgba(0, 0, 0, 0.19),
+              0 13px 25px 0 rgba(0, 0, 0, 0.3);
+}
+
+.shadow-elevation-4 {
+  box-shadow: 0 14px 12px 0 rgba(0, 0, 0, 0.17),
+              0 20px 40px 0 rgba(0, 0, 0, 0.3);
+}
+
+.shadow-elevation-5 {
+  box-shadow: 0 17px 17px 0 rgba(0, 0, 0, 0.15),
+              0 27px 55px 0 rgba(0, 0, 0, 0.3);
+}
+</style>