Remove third_party/polymer from .gitignore

third_party/polymer/v1_0/components/paper-styles/demo.css

-/**
-@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
-
-*/
-body {
-  font-family: 'Roboto', 'Noto', sans-serif;
-  font-size: 14px;
-  margin: 0;
-  padding: 24px;
-}
-
-section {
-  padding: 20px 0;
-}
-
-section > div {
-  padding: 14px;
-  font-size: 16px;
-}