Import Polymer 0.8 and several key elements.

third_party/polymer/v0_8/components/polymer/src/lib/expr/focus.html

Index: third_party/polymer/v0_8/components/polymer/src/lib/expr/focus.html
diff --git a/third_party/polymer/v0_8/components/polymer/src/lib/expr/focus.html b/third_party/polymer/v0_8/components/polymer/src/lib/expr/focus.html
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index 0000000000000000000000000000000000000000..f3d5be8649e7621952def9802fb4f8470629f85c
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+++ b/third_party/polymer/v0_8/components/polymer/src/lib/expr/focus.html
@@ -0,0 +1,22 @@
+<!--
+@license
+Copyright (c) 2014 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
+-->
+<script>
+
+  Base._addFeature({
+
+    init: function() {
+      if (this.focusable) {
+        this.tabIndex = 0;
+      }
+    }
+
+  });
+
+</script>